Video signal processing circuit, video signal display apparatus, and video signal recording apparatus

ABSTRACT

A video signal processing circuit that uses a prescribed clock signal to process a digitized composite video signal. A clock generating means ( 2 ) generates the prescribed clock signal; a burst phase detecting means ( 3 ) detects color subcarrier phase information (p) in each line of the composite video signal; a phase difference calculation means ( 4 ) finds the phase difference between phase information (p) from the burst phase detecting means and a prescribed reference phase; a sampling phase conversion means ( 8 ) corrects the sampling phase of the composite video signal according to phase corrections (Δb, Δt) obtained from the phase difference calculation means ( 4 ); a Y/C separation means ( 9 ) separates the luminance and chrominance signals from the composite video signal output from the sampling phase conversion means ( 8 ). Excellent two- or three-dimensional Y/C separation can be obtained regardless of the television broadcast system, even from a non-standard signal.

FIELD OF THE INVENTION

The present invention relates to the processing of a received compositevideo signal to separate the luminance and chrominance signals (Y/Cseparation), more particularly to video signal processing that convertsthe sampling phase of the composite video signal.

BACKGROUND ART

There are various standard analog color television (TV) broadcastsystems, including the National Television System Committee (NTSC)system used in the United States and Japan, the Phase Alternation byLine (PAL) system used mainly in western Europe, and the SequentialColeur avec Memoire (SECAM) system used in France and elsewhere. Due tothe spread of video tape recorders (VTRs) and video games, non-standardvideo signals other than the signals (standard signals) used in theabove standard television broadcast systems can also be found. In recentyears, video signal processing devices that perform digital signalprocessing of standard and non-standard video signals used in severaldifferent types of television broadcast systems have been developed.

In such digital video signal processing, the analog video signal isconverted to a digital signal (A/D conversion) by use of a prescribedsampling clock, and then converted from a composite signal to aluminance signal (Y signal) and a chrominance signal (C signal) by aprocess referred to as Y/C separation.

Conventional video signal processing circuits perform Y/C separation bygenerating a burst locked clock based on the color subcarrier frequency(fsc) of a burst signal imposed on the blanking interval of thecomposite signal (as a reference signal for the chrominance signal phaseand amplitude; see, for example, Patent Document No. 1).

To support multiple television broadcast systems, another type of videosignal processing circuit performs Y/C separation by converting acomposite video signal that has been sampled on a single common free runclock to sampling data with a frequency four times that of the burstlocked color subcarrier frequency (hereinafter, 4fsc; see, for example,Patent Documents No. 2 and No. 3).

A general method of Y/C separation uses a horizontal frequencyseparation filter based on the frequency band of the chrominance signal(hereinafter, one-dimensional Y/C separation). In the NTSC system,two-dimensional Y/C separation and three-dimensional Y/C separation canprovide higher picture quality: two-dimensional separation uses a linecomb filter, exploiting the fact that the phase of the color subcarrieris inverted on alternate horizontal scanning lines (see, for example,Patent Document No. 4); three-dimensional Y/C separation uses a framecomb filter, exploiting the fact that the color subcarrier phase of thesame horizontal scanning line is inverted in alternate frames (see, forexample, Patent Document No. 5).

Two-dimensional or three-dimensional Y/C separation is based on thecorrelation between lines or frames (line-to-line or frame-to-framecolor subcarrier phase relationship). The Y/C separation process uses,for example, the property of the standard NTSC signal that the colorsubcarrier phase inverts (the phase changes by 180°) at the horizontalperiod (the line-to-line period) or the frame period.

In a number of television broadcast systems the burst lockedline-to-line or frame-to-frame phase relationship differs from therelationship in the NTSC system: in the NTSC-4.43 system and PAL system,for example, the phase of the video signal does not invert; in thenon-standard signals used in VTRs and video games, the line-to-linephase relationship decays and the phase does not always invert by 180°.If the line-to-line difference in the color subcarrier phase is notexactly 180°, two-dimensional or three-dimensional Y/C separation cannotseparate the luminance and chrominance signals accurately. The reducedaccuracy results in dot crawl and other picture quality problems.

Since two-dimensional Y/C separation or three-dimensional Y/C separationcannot always be applied to the composite signals of those televisionbroadcast systems that lack the above color subcarrier phaserelationship, or to non-standard signals in which the color subcarrierphase becomes displaced, one-dimensional Y/C separation ortwo-dimensional Y/C separation is performed selectively, according tothe standard or non-standard signal of each television broadcast system(see, for example, Patent Documents No. 3. No. 6, and No. 7).

Patent Document No. 1: Japanese Patent Application Publication No.H10-164618 (FIG. 1)

Patent Document No. 2: Japanese Patent Application Publication No.2001-112016 (FIG. 1)

Patent Document No. 3: Japanese Patent Application Publication No.2002-315018 (FIGS. 1 and 6)

Patent Document No. 4: Japanese Patent No. 2566342 (FIG. 1)

Patent Document No. 5: Japanese Patent Application Publication No.H1-174088 (FIG. 1)

Patent Document No. 6: Japanese Patent Application Publication No.H7-131819 (FIG. 1)

Patent Document No. 7: Japanese Patent Application Publication No.2003-92766 (FIG. 1)

DISCLOSURE OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

The conventional video signal processing circuits described above cannotperform two-dimensional Y/C separation or three-dimensional Y/Cseparation based on the line-to-line or frame-to-frame color subcarrierphase relationship of non-standard signals in which the color subcarrierphase becomes displaced, or even standard signals if the standardsystems belong to television broadcast systems lacking the colorsubcarrier phase inversion of the NTSC system, so good Y/C separation isnot obtainable, picture quality problems such as luminance-chrominancecrosstalk and dot crawl occur, and the video signal cannot be displayedor recorded without some loss of picture quality.

The present invention addresses the problems described above, with anobject of providing video signal processing circuits, video signaldisplay devices, and video signal recording devices that can performexcellent two-dimensional or three-dimensional Y/C separation regardlessof the line-to-line or frame-to-frame phase relationship of thecomposite video signal and regardless of the use of non-standardsignals, and can prevent picture quality degradation after Y/Cseparation.

Means of Solution of the Problems

The present invention provides a video signal processing circuit thatsamples an analog composite video signal, converts it to a digitalsignal, and processes it by using a prescribed clock signal, comprising:

a clock generating means generating the prescribed clock signal;

a phase detecting means detecting color subcarrier phase information ineach line of the composite video signal;

a phase difference calculation means calculating a phase differencebetween phase information from the phase detecting means and aprescribed reference phase, calculating a phase correction from thephase difference, and outputting the phase correction;

a sampling phase conversion means correcting the phase at which thecomposite video signal is sampled according to the phase correctionoutput from the phase difference calculation means; and

a luminance-chrominance (Y/C) separation means separating a luminancesignal and a chrominance signal from the composite video signal outputfrom the sampling phase conversion means.

EFFECT OF THE INVENTION

According to the present invention, line-to-line or frame-to-framedifferences in the color subcarrier phase are corrected to align thecolor subcarrier phase with sampling points having the phaserelationship used in two-dimensional or three-dimensional Y/Cseparation, whereby excellent two- or three-dimensional Y/C separationcan be obtained from signals in a plurality of television broadcastsystems, regardless of the line-to-line or frame-to-frame phaserelationship, or regardless of the use of non-standard signals,producing the effect that degradation of picture quality after Y/Cseparation can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an example of the structure of a videosignal processing circuit according to a first embodiment of the presentinvention;

FIG. 2 is a block diagram showing an example of the structure of theburst phase detecting means in the video signal processing circuitaccording to the first embodiment of the invention;

FIG. 3 is a block diagram showing an example of the structure of thephase difference calculation means in the video signal processingcircuit according to the first embodiment of the invention;

FIG. 4 is a block diagram showing an example of the structure of thesampling phase conversion means in the video signal processing circuitaccording to the first embodiment of the invention;

FIG. 5 is a block diagram showing an example of the structure of thephase conversion filters in the video signal processing circuitaccording to the first embodiment of the invention;

FIG. 6 is a block diagram showing an example of the structure of the Y/Cseparation means in the video signal processing circuit according to thefirst embodiment of the invention;

FIG. 7 is a diagram illustrating the line-to-line color subcarrier phaseafter the sampling phase conversion in the video signal processingcircuit according to the first embodiment of the invention;

FIGS. 8(a)-(c) are diagrams illustrating sampling phase conversionaccording to the first embodiment of the invention in more detail;

FIG. 9 is a block diagram showing another example of the structure ofthe phase conversion filters in the video signal processing circuitaccording to the first embodiment of the invention;

FIG. 10 is a block diagram showing yet another example of the structureof the phase conversion filters in the video signal processing circuitaccording to the first embodiment of the invention;

FIG. 11 is a block diagram showing an example of the structure of avideo signal processing circuit according to a second embodiment of theinvention;

FIG. 12 is a block diagram showing an example of the structure of thephase difference calculation means in the video signal processingcircuit according to the second embodiment of the invention;

FIG. 13 is a block diagram showing an example of the structure of thesampling phase conversion means in the video signal processing circuitaccording to the second embodiment of the invention;

FIG. 14 is a block diagram showing an example of the structure of avideo signal processing circuit according to a third embodiment of theinvention;

FIG. 15 is a block diagram showing an example of the structure of thephase difference calculation means in the video signal processingcircuit according to the third embodiment of the invention;

FIGS. 16(a)-(c) are diagrams illustrating a clock phase correctionaccording to the third embodiment of the invention;

FIG. 17 is a block diagram showing an example of the structure of theline delay selection means in the video signal processing circuitaccording to the third embodiment of the invention;

FIG. 18 is a block diagram showing an example of the structure of avideo signal processing circuit according to a fourth embodiment of theinvention;

FIG. 19 is a block diagram showing an example of the structure of theburst signal phase detecting means in the video signal processingcircuit according to the fourth embodiment of the invention;

FIG. 20 is a block diagram showing an example of the structure of avideo signal processing circuit according to a fifth embodiment of theinvention;

FIG. 21 is a block diagram showing an example of the structure of thephase difference calculation means in the video signal processingcircuit according to the fifth embodiment of the invention;

FIG. 22 is a block diagram showing an example of the structure of theframe sampling phase conversion means in the video signal processingcircuit according to the fifth embodiment of the invention;

FIG. 23 is a block diagram showing an example of the structure of theY/C separation means in the video signal processing circuit according tothe fifth embodiment of the invention;

FIG. 24 is a block diagram showing another example of the structure ofthe phase difference calculation means in the video signal processingcircuit according to the fifth embodiment of the invention;

FIG. 25 is a block diagram showing another example of the structure ofthe frame sampling phase conversion means in the video signal processingcircuit according to the fifth embodiment of the invention;

FIG. 26 is a block diagram showing an example of the structure of avideo signal processing circuit according to a sixth embodiment of theinvention;

FIG. 27 is a block diagram showing an example of the structure of avideo signal display device according to a seventh embodiment of theinvention;

FIG. 28 is a block diagram showing another example of the structure ofthe video signal display device according to the seventh embodiment ofthe invention;

FIG. 29 is a block diagram showing yet another example of the structureof the video signal display device according to the seventh embodimentof the invention;

FIG. 30 is a block diagram showing still another example of thestructure of the video signal display device according to the seventhembodiment of the invention;

FIG. 31 is a block diagram showing an example of the structure of avideo signal display device according to an eighth embodiment of theinvention;

FIG. 32 is a block diagram showing another example of the structure ofthe video signal display device according to the eighth embodiment ofthe invention;

FIG. 33 is a block diagram showing an example of the structure of avideo signal recording device according to a ninth embodiment of theinvention;

FIG. 34 is a block diagram showing another example of the structure ofthe video signal recording device according to the ninth embodiment ofthe invention;

FIG. 35 is a block diagram showing yet another example of the structureof the video signal recording device according to the ninth embodimentof the invention;

FIG. 36 is a block diagram showing still another example of thestructure of the video signal recording device according to the ninthembodiment of the invention;

FIG. 37 is a block diagram showing an example of the structure of avideo signal recording device according to a tenth embodiment of theinvention; and

FIG. 38 is a block diagram showing another example of the structure ofthe video signal recording device according to the tenth embodiment ofthe invention.

EXPLANATION OF REFERENCE CHARACTERS

1 A/D conversion means (ADC), 2 clock generating means, 3 burst phasedetecting means, 4 phase difference calculation means, 5 sync separationmeans, 6, 6 a, 6 b, 6 c timing signal generating means, 7 broadcastsystem setting means, 8 sampling phase conversion means, 9 Y/Cseparation means, 10 burst signal phase detecting means, 11 burst signalextraction means, 12 phase comparison means, 13 loop filter, 14numerically controlled oscillator (NCO), 15 sinewave read-only memory(ROM), 21 to 24 delaying means, 25 selection means, 26 phase errorcalculation means, 27 phase correction conversion means, 30 to 33one-line delaying means, 34 delay compensation means, 35 selectionmeans, 36 phase conversion filter, 37 delay compensation means, 38 phaseconversion filter, 40 coefficient generating means, 41a to 41h one-clockdelaying means, 42 amplifying circuit, 43 adder, 44 one-clock delayingmeans, 45 selection means, 46-1 to 46-N correction delaying means, 47selection means, 48 coefficient generating means, 49 interpolationfilter, 50 vertical chrominance signal extraction filter, 51 horizontalchrominance signal extraction filter, 52 horizontal-vertical chrominancesignal extraction filter, 53 correlation determination means, 54selection means, 55 subtractor, 60 phase difference calculation means,61 sampling phase conversion means, 62 phase error calculation means, 63phase correction conversion means, 64 to 66 phase conversion filters, 70clock phase correction means, 71 phase difference calculation means, 72line delay selection means, 73 phase error calculation means, 74 phasecorrection conversion means, 75a to 75d one-line delaying means, 76delay compensation means, 77 selection means, 81 phase differencecalculation means, 82 frame sampling phase conversion means, 83 Y/Cseparation means, 84 one-frame delaying means, 85 phase errorcalculation means, 86 phase correction conversion means, 87 one-framedelaying means, 88 delay compensation means, 89 phase conversion means,90 subtractor, 91 bandpass filter (BPF), 92 subtractor, 93 phase errorcalculation means, 94 phase correction conversion means, 96, 96 phaseconversion means, 100 input terminal, 101, 102, 103, 104, 105 outputterminals, 110 color demodulating means, 200, 202 display processingmeans, 201 display means, 300, 302 recording signal processing means,301 recording means

BEST MODE OF PRACTICING THE INVENTION

A characterizing feature of a video signal processing circuit embodyingthe present invention is that it detects color subcarrier phaseinformation from the burst phase in each line of the composite videosignal, takes the phase difference between the phase information and aprescribed reference phase, corrects the sampling phase of the compositevideo signal according to the phase difference, and then separates theluminance and chrominance signals.

First Embodiment

FIG. 1 is a block diagram showing an example of the structure of a videosignal processing circuit according to a first embodiment of theinvention. The video signal processing circuit in FIG. 1 comprises anA/D conversion means (analog-to-digital converter or ADC) 1, a clockgenerating means 2, a burst phase detecting means 3, a phase differencecalculation means 4, a sync separation means 5, a timing signalgenerating means 6, a broadcast system setting means 7, a sampling phaseconversion means 8, a Y/C separation means 9, an input terminal 100, anda pair of output terminals 101, 102.

Clock Generating Means 2

The clock generating means 2 generates a clock with a prescribedfrequency X and supplies it to the A/D conversion means 1, burst phasedetecting means 3, phase difference calculation means 4, sync separationmeans 5, timing signal generating means 6, sampling phase conversionmeans 8, and Y/C separation means 9.

The clock with frequency X generated by the clock generating means 2 isa free run clock having a single common frequency X for a plurality oftelevision broadcast systems. The frequency X is an integer multiple of13.5 MHz, which is a reference frequency calculated as a common multipleof the horizontal frequency in different television broadcast systemsand which can thus be shared: for example, X=27 MHz.

The A/D conversion means 1, burst phase detecting means 3, phasedifference calculation means 4, sync separation means 5, timing signalgenerating means 6, sampling phase conversion means 8, and Y/Cseparation means 9 all operate on this single clock with a frequency Xof 27 MHz.

A/D Conversion Means 1

The A/D conversion means 1 samples an analog composite video signalinput from the input terminal 100 on a sampling clock generated by theclock generating means 2, converts the sampled signal to a digitalsignal, and outputs it to the burst phase detecting means 3, syncseparation means 5, and sampling phase conversion means 8.

The input terminal 100 receives composite video signals conforming todifferent television broadcast systems such as NTSC, PAL, and SECAM.

Sync Separation Means 5

The sync separation means 5 separates a vertical synchronizing (sync)signal and a horizontal sync signal from the digital composite signaloutput from the A/D conversion means 1 and outputs the sync signals tothe timing signal generating means 6.

Timing Signal Generating Means 6

The timing signal generating means 6 generates a timing signal based onthe sync signals output from the sync separation means 5, and outputsthe timing signal to the phase difference calculation means 4 andsampling phase conversion means 8. In this embodiment, it generates atiming signal hb, based on the horizontal sync signal, that indicatessampling points in certain positions relative to the horizontal syncsignal: for example, sampling positions in the burst signal interval inthe horizontal blanking interval.

Broadcast System Setting Means 7

The broadcast system setting means 7 specifies a television broadcastsystem selected by the user, for example, and outputs informationconcerning the specified television broadcast system to the burst phasedetecting means 3, phase difference calculation means 4, sampling phaseconversion means 8, and Y/C separation means 9, in the form of anidentification signal indicating the selected television broadcastsystem, such as NTSC, PAL, or SECAM, or a signal indicating thecorresponding color subcarrier frequency, as a television broadcastsystem specification signal.

The A/D conversion means 1, clock generating means 2, sync separationmeans 5, and timing signal generating means 6, which do not receive thetelevision broadcast system specification signal from the broadcastsystem setting means 7, operate in the same manner regardless of whetherNTSC, PAL, SECAM, or any other television broadcast system is selected.

The television broadcast system need not be specified by user selection;it may be determined automatically from, for example, the colorsubcarrier frequency (fsc) of the burst signal of the input compositesignal or the period of the vertical or horizontal sync signal. Thebroadcast system setting means 7 may be configured to make the automaticdetermination.

Burst Phase Detecting Means 3

The burst phase detecting means 3 detects the burst phase in each lineof the composite signal output from the A/D conversion means 1 andoutputs color subcarrier phase information p for the line to the phasedifference calculation means 4.

FIG. 2 is a block diagram showing an example of the structure of theburst phase detecting means 3. As shown in the drawing, the burst phasedetecting means 3 comprises a burst signal extraction means 11, a phasecomparison means 12, a loop filter 13, a numerically controlledoscillator (NCO) 14, and a sinewave read-only memory (ROM) 15. The NCO14 is a digital oscillator, analogous to a voltage controlled oscillator(VCO) of the type used in analog signal processing.

The burst signal extraction means 11 extracts a burst signal imposed onthe blanking interval of the composite signal input from the A/Dconversion means 1 and outputs the burst signal to the phase comparisonmeans 12. The phase comparison means 12 compares the phases of the burstsignal output from the burst signal extraction means 11 and a referencesignal with the color subcarrier frequency fsc output from the sinewaveROM 15, and outputs a signal corresponding to the phase difference tothe loop filter 13. The loop filter 13 smoothes the signal output fromthe phase comparison means 12 and outputs a smoothed phase comparisonresult to the NCO 14.

The NCO 14 integrates the smoothed phase comparison result output fromthe loop filter 13 over time, generates phase information p for theburst signal, and outputs it to the phase difference calculation means4. The sinewave ROM 15 generates the reference signal with the colorsubcarrier frequency fsc in accordance with the phase information p andoutputs this signal to the phase comparison means 12.

The NCO 14 acquires phase lock and continuously outputs phaseinformation for generating the reference signal with the colorsubcarrier frequency fsc, that is, color subcarrier phase information ofthe current burst signal in the input composite signal, as colorsubcarrier phase information p for the current line.

Phase Difference Calculation Means 5

The phase difference calculation means 4 calculates line-to-line phaseerrors between the target line and lines thereabove and therebelow inaccordance with the color subcarrier phase information p, obtains phasecorrections Δb and Δt from the phase errors, and outputs the phasecorrections to the sampling phase conversion means 8.

FIG. 3 is a block diagram showing an example of the structure of thephase difference calculation means 4. As shown in the drawing, the phasedifference calculation means 4 comprises delaying means 21, 22, 23, 24,a selection means 25, a phase error calculation means 26, and a phasecorrection conversion means 27.

In the phase difference calculation means 4 shown in FIG. 3, the phaseinformation p output from the burst phase detecting means 3 is input todelaying means 21 and the phase error calculation means 26. The timingsignal hb output from the timing signal generating means 6 is input todelaying means 21 to 24. The television broadcast system specificationsignal output from the broadcast system setting means 7 is input to theselection means 25 and phase correction conversion means 27.

Delaying means 21 delays the phase information p by one line inaccordance with timing signal hb, and outputs the delayed information tothe delaying means 22 and selection means 25. Delaying means 22 delaysthe phase information p input from delaying means 21 by one more line inaccordance with timing signal hb, and outputs the delayed information todelaying means 23 and the selection means 25. Delaying means 23 delaysthe phase information p input from the delaying means 22 by yet one moreline in accordance with timing signal hb, and outputs the delayedinformation to delaying means 24. Delaying means 24 delays the phaseinformation p input from delaying means 23 by one further line inaccordance with timing signal hb, and outputs the delayed information tothe selection means 25.

Timing signal hb is a timing signal (a burst gate signal, for example)indicating the position of the burst signal interval, based on thehorizontal sync signal, and is used to delay the burst signal phaseinformation p by one line.

The delaying means 22 to 24 each delay the phase information p inputfrom the burst phase detecting means 3 successively by one line inaccordance with timing signal hb.

From the one-line-delayed, two-line-delayed, and four-line-delayed phaseinformation p supplied by delaying means 21, 22, and 24, the selectionmeans 25 selects two items of phase information p in accordance with thetelevision broadcast system specification signal output from thebroadcast system setting means 7, and outputs phase information p fortwo lines to the phase error calculation means 26.

The selection means 25 selects phase information so that the output ofthe selection means 25 and the output of the burst phase detecting means3 (input of the delaying means 21) constitute phase information p forthree lines: the target line and lines thereabove and therebelow. Theselected phase information is input to the phase error calculation means26. This enables the Y/C separation means 9 to carry out two-dimensionalY/C separation by using signals from lines with opposite phases.

The phase error calculation means 26 calculates the line-to-line phaseerrors δb, δt to be corrected from the three-line phase information pobtained from the burst phase detecting means 3 and selection means 25,and outputs them to the phase correction conversion means 27.

The phase correction conversion means 27 converts the phase-errors δband δt obtained from the phase error calculation means 26 to phasecorrections Δb and Δt, and outputs them to the sampling phase conversionmeans 8.

Since the phase information p indicates an angle, where one period ofthe color subcarrier corresponds to 2π, the conversion process performedby the phase correction conversion means 27 converts the phase errors δband δt output from the phase error calculation means 26 to valuesrepresenting time with reference to one period of the clock with afrequency X of 27 MHz, (time represented as a multiple of the period ofclock with frequency X) If the change ω expressed in color subcarrierphase angle per clock period is 2π×fsc/X, where fsc is the colorsubcarrier frequency, the phase corrections Δb and Δt obtained byconversion of the phase errors δb and δt are expressed as follows:Δb=δb/ωΔt=δt/ωIf the phase errors δb and δt range from −π to +π, the phase correctionsΔb and Δt range from −X/(2×fsc) to X/(2×fsc)

Sampling Phase Conversion Means 8

The sampling phase conversion means 8 obtains, for example, digitalcomposite signals for three lines (the target line and lines thereaboveand therebelow) from the A/D conversion means 1 as the signals to beused for Y/C separation, corrects the phases of the composite signals ofthe lines thereabove and therebelow by phase corrections Δt and Δbobtained from the phase difference calculation means 4, and outputs thecomposite signal DM of the target line and phase-corrected compositesignals DT and DB of the lines thereabove and therebelow to the Y/Cseparation means 9.

Through this processing, the sampling phase conversion means 8 correctsthe sampling phase of the digital video signal, after A/D conversion ona single free run clock, in accordance with phase errors with respect toa reference value obtained from the phase information of the burstsignal, so that a predetermined phase relationship is established.

FIG. 4 is a block diagram showing an example of the structure of thesampling phase conversion means 8. As shown in the drawing, the samplingphase conversion means 8 comprises one-line delaying means 30, 31, 32,33, a delay compensation means 34, a selection means 35, a phaseconversion filter 36, a delay compensation means 37, and another phaseconversion filter 38.

In the sampling phase conversion means 8 shown in FIG. 4, the compositesignal output from the A/D conversion means 1 is input to one-linedelaying means 30 and delay compensation means 34. The timing signal hboutput from the timing signal generating means 6 is input to one-linedelaying means 30 to 33. The television broadcast system specificationsignal output from the broadcast system setting means 7 is input to theselection means 35. The phase correction Δb output from the phasedifference calculation means 4 is input to the first phase conversionfilter 36, and the phase correction Δt output from the phase differencecalculation means 4 is input to the second phase conversion filter 38.

The delay compensation means 34 outputs the composite signal obtainedfrom the A/D conversion means 1 to phase conversion filter 36, withcompensation for the delay of the signal output from the selection means35.

The one-line delaying means 30 delays the input composite signal by oneline in accordance with the timing signal hb based on the horizontalsync signal, and outputs the delayed signal to the one-line delayingmeans 31 and selection means 35. The one-line delaying means 31 delaysthe composite signal output from the one-line delaying means 30 by onemore line in accordance with timing signal hb, and outputs the delayedsignal to the one-line delaying means 32 and selection means 35. Theone-line delaying means 32 delays the composite signal output from theone-line delaying means 31 by yet one more line in accordance withtiming signal hb, and outputs the delayed signal to the one-linedelaying means 33. The one-line delaying means 33 delays the compositesignal output from the one-line delaying means 32 by still another linein accordance with timing signal hb, and outputs the delayed signal tothe selection means 35.

The one-line delaying means 30 to 33 successively delay the compositesignal input from the A/D conversion means 1 by one line each inaccordance with timing signal hb.

The selection means 35 selects two signals from the output signals ofthe one-line delaying means 30, 31, 33, in accordance with thetelevision broadcast system specified by the broadcast system settingmeans 7, and outputs one of the two signals to delay compensation means37 and the other to the second phase conversion filter 38.

The delay compensation means 37 outputs the composite signal obtainedfrom the selection means 35 as composite signal DM to the Y/C separationmeans 9, with compensation for the signal delays of the other compositesignals output from the phase conversion filters 36 and 38.

Phase conversion filter 36 corrects the phase of the composite signaloutput from delay compensation means 34 in accordance with the phasecorrection Δb given by the phase difference calculation means 4, andoutputs the corrected signal as composite signal DB to the Y/Cseparation means 9. Phase conversion filter 38 corrects the phase of thecomposite signal output from the selection means 35 in accordance withthe phase correction Δt given by the phase difference calculation means4, and outputs the corrected signal as composite signal DT to the Y/Cseparation means 9.

Phase corrections Δt and Δb are phase corrections with respect to thecolor subcarrier phase on line k, given for the lines thereabove andtherebelow. The phase corrections have been converted to values based onthe period of the clock with a frequency X of 27 MHz. The signals of thelines thereabove and therebelow input to the phase conversion filters 36and 38 are delayed by Δb and Δt respectively, thereby converting andcorrecting the sampling phase.

FIG. 5 is a block diagram showing an example of the structure of thephase conversion filters 36 and 38. The phase conversion filter 36 or 38shown in the drawing comprises a coefficient generating means 40,one-clock delaying means 41 a to 41 h, an amplifying circuit 42, anadder 43, a one-clock delaying means 44, and a selection means 45.

The phase conversion filter 36 or 38 shown in FIG. 5 is provided as atype of linear phase filter referred to as a finite impulse response(FIR) filter, and is given a group delay corresponding to the phasecorrection Δn (Δb or Δt). The filter corrects the phase of the compositesignal by giving a delay Δn corresponding to a phase correction smallerthan one clock period. The phase conversion filter 36 or 38 shown in thedrawing has eight taps.

In the phase conversion filter 36 or 38 shown in FIG. 5, the coefficientgenerating means 40 generates filter coefficients g0 to g7 of the FIRfilter with a group delay corresponding to the phase correction Δn, inaccordance with the phase correction Δn (Δb or Δt) input from the phasedifference calculation means 4, and outputs them to the amplifyingcircuit 42. It may be configured as a ROM, for example, and the filtercoefficients may be generated by using the value of the phase correctionΔn as an address.

The one-clock delaying means 41 a to 41 h delay the composite signalinput from delay compensation means 34 or selection means 35 by oneclock period each. The outputs of one-clock delaying means 41 a to 41 hare supplied to the amplifying circuit 42. The output of one-clockdelaying means 41e is also supplied to the selection means 45.

The amplifying circuit 42 comprises eight amplifiers, which receive thesignals output from the one-clock delaying means 41 a to 41 h and usethe filter coefficients g0 to g7 given by the coefficient generatingmeans 40 as their respective gains. The amplifiers multiply thecomposite signals input from the one-clock delaying means 41 a to 41 hby the corresponding filter coefficients g0 to g7, and output theresults to the adder 43.

The adder 43 sums the values output from the amplifying circuit 42, andoutputs the result to the one-clock delaying means 44. The one-clockdelaying means 44 supplies the output of the adder 43 to the selectionmeans 45 with a one-clock delay.

If the phase correction Δn (Δb or Δt) output from the phase differencecalculation means 4 is zero (if phase correction is not required), theselection means 45 selects the delay-adjusted output of one-clockdelaying means 41e. If the phase correction Δn is not zero (if phasecorrection is required), the selection means 45 selects the output ofone-clock delaying means 44. The selected output is supplied to the Y/Cseparation means 9 as a phase-converted (phase-corrected) compositesignal DB or DT.

Y/C Separation Means 9

The Y/C separation means 9 is a two-dimensional Y/C separation meansutilizing a line comb filter. Through two-dimensional Y/C separation, itextracts the C signal from the composite signals DB, DM, and DT inputfrom the sampling phase conversion means 8 in accordance with the colorsubcarrier frequency fsc of the television broadcast system specified bythe broadcast system setting means 7, separates the Y signal and Csignal, outputs the C signal to output terminal 101, and outputs the Ysignal to output terminal 102.

The phases of the composite signals DB, DM, and DT input from thesampling phase conversion means 8 have been corrected so that compositesignals DB and DM have opposite color subcarrier phases and compositesignal DM and DT have opposite color subcarrier phases. Accordingly, thesampling data on the three lines of composite signals DB, DM, and DT arealigned with sampling points where the color subcarrier phaserelationship used by the Y/C separation means 9 is established.

FIG. 6 is a block diagram showing an example of the structure of the Y/Cseparation means 9. As shown in the drawing, the Y/C separation means 9comprises a vertical chrominance signal extraction filter 50, ahorizontal chrominance signal extraction filter 51, ahorizontal-vertical chrominance signal extraction filter 52, acorrelation determination means 53, a selection means 54, and asubtractor 55.

In the Y/C separation means 9 shown in FIG. 6, the composite signals DT,DM, and DB for three lines obtained from the sampling phase conversionmeans 8 are supplied to the vertical chrominance signal extractionfilter 50, horizontal-vertical chrominance signal extraction filter 52,and correlation determination means 53. Composite signal DM is alsosupplied to the horizontal chrominance signal extraction filter 51 andsubtractor 55. The television broadcast system specification signalinput from the broadcast system setting means 7 is supplied to thehorizontal chrominance signal extraction filter 51 andhorizontal-vertical chrominance signal extraction filter 52.

The vertical chrominance signal extraction filter 50 extracts achrominance signal from the input composite signals DT, DM, and DB,assuming that the three input lines exhibit vertical picturecorrelation, and outputs the extracted signal to the selection means 54.The horizontal chrominance signal extraction filter 51 extracts achrominance signal from input composite signal DM, assuming a horizontalpicture correlation, and outputs the extracted signal to the selectionmeans 54. The horizontal-vertical chrominance signal extraction filter52 extracts a chrominance signal from input composite signals DT, DM,and DB, assuming that the three input lines have horizontal and verticalpicture correlations, and outputs the extracted signal to the selectionmeans 54.

In accordance with the television broadcast system specification signalinput from the broadcast system setting means. 7, the horizontalchrominance signal extraction filter 51 and horizontal-verticalchrominance signal extraction filter 52 use a filter corresponding tothe color subcarrier frequency fsc of the specified television broadcastsystem.

From the input composite signals DT, DM, DB, the correlationdetermination means 53 detects vertical and horizontal picturecorrelations of the three input lines at the sampling points ofcomposite signal DM, and outputs the result to the selection means 54.

Based on the correlations detected by the correlation determinationmeans 53, the selection means 54 selects one of the signals output fromthe vertical chrominance signal extraction filter 50, horizontalchrominance signal extraction filter 51, and horizontal-verticalchrominance signal extraction filter 52 according to its picturecorrelation strengths, and outputs the signal to output terminal 102(FIG. 1) and subtractor 55 as the C signal (chrominance signal)separated from the composite signal. If the horizontal correlation isweak, the output signal of the vertical chrominance signal extractionfilter 50 is selected. If the vertical correlation is weak, the outputsignal of the horizontal chrominance signal extraction filter 51 isselected. Otherwise, the output signal of the 52 is selected.

The subtractor 55 subtracts the C signal output by the selection means54 from input composite signal DM to obtain the Y signal (luminancesignal), and outputs the separated Y signal to output terminal 101 (FIG.1).

Operation when an NTSC Composite Signal Is Input

When an NTSC composite video signal is input to the input terminal 100,the following operations are performed. Since the NTSC system has beenspecified by the broadcast system setting means 7, the NCO 14 in theburst phase detecting means 3 outputs phase information p for an NTSCsignal with color subcarrier frequency fsc(NTSC), and the sinewave ROM15 outputs an NTSC reference signal with color subcarrier frequencyfsc(NTSC) to the phase comparison means 12.

The color subcarrier phase of the NTSC composite signal inverts by 180°(=π) on alternate lines. The color subcarrier phase of line k isinverted in lines k−1 and k+1. The Y/C separation means 9 separates theY and C signals by two-dimensional Y/C separation, exploiting the factthat the color subcarrier phase is inverted on alternate lines.

In the phase difference calculation means 4, the selection means 25selects the color subcarrier phase information p(k−1) for line k−1, oneline above line k on the screen, and the color subcarrier phaseinformation p(k+1) for line k+1, one line below line k on the screen.The phase error calculation means 26 receives the phase informationp(k−1) and p(k+1) together with the color subcarrier phase informationp(k) for line k.

The phase error calculation means 26 is thus supplied with the phaseinformation p(k+1) output from the burst phase detecting means 3 asphase information for line k+1, the one-line-delayed phase informationp(k) output from delaying means 21 as phase information for line k, andthe two-line-delayed phase information p(k−1) output from delaying means22 as phase information for line k−1.

In consideration of the line-to-line phase inversion of π, the phaseerror calculation means 26 in the phase difference calculation means 4calculates the phase error δb with respect to the phase information p(k)for line k which is to be corrected in the signal of line k+1 one linebelow as follows,δb=p(k+1)−p(k)−πand calculates the phase error δt with respect to the phase informationp(k) for line k which is to be corrected in the signal of line k−1 oneline above as followsδt=p(k−1)−p(k)+πwhere −π and +π are both fixed phase values and −p(k)−π and −p(k)+π areequivalent to reference phases with respect to line k on lines k+1 andk−1, respectively. Phase errors δb and δt are obtained as phasedifferences between the phase information p(k+1) and p(k−1) of lines k+1and k−1 and the reference phase with respect to line k.

For a standard NTSC input signal with a line-to-line phase inversion of180°, phase errors δb and δt are both zero. For a non-standard signal,values equivalent to the phase difference are obtained as phase errorsδb and δt.

The phase correction conversion means 27 in the phase differencecalculation means 4 obtains the amount of change ω(NTSC) in NTSC colorsubcarrier phase per clock in accordance with the NTSC color subcarrierfrequency fsc(NTSC) as follows,ω(NTSC)=2πfsc(NTSC)/Xand converts phase errors δb and at to phase corrections δb and Δt asfollows:Δb=δb/ω(NTSC)Δt=δt/ω(NTSC)

In the sampling phase conversion means 8, when the composite signal ofline k+1 (the line immediately below line k on the screen) is suppliedthrough delay compensation means 34 to phase conversion filter 36, theselection means 35 selects the composite signal of line k suppliedthrough one-line delaying means 30 and the composite signal of line k−1(the line immediately above line k on the screen) supplied throughone-line delaying means 31. The composite signal of line k is output todelay compensation means 37, and the composite signal of line k−1 isoutput to phase conversion filter 38.

The phase conversion filters 36 and 38 configured as shown in FIG. 5correct the phases of the composite signals of lines k+1 and k−1 inaccordance with phase corrections Δb and Δt, respectively. The compositesignal DT of line k−1 with its phase corrected by phase conversionfilter 38, the composite signal DM of line k with a compensating delayapplied by delay compensation means 37, and the composite signal DB ofline k+1 with its phase corrected by phase conversion filter 36 areoutput to the Y/C separation means 9.

FIG. 7 shows an example of the sampling phase correction applied by thephase conversion filters 36 and 38 in the NTSC system. The compositesignals of lines k+1 and k−1 supplied to the filters, represented bydotted lines in FIG. 7, are corrected by the phase corrections Δb and Δtobtained from conversion of the phase errors δb and δt, so aftersampling phase conversion, the composite signals of lines k+1 and k−1are corrected to signals with phases represented by the solid lines.

As shown in FIG. 7, the sampling data of the composite signal DT of linek−1 and the composite signal DB of line k+1 are corrected so that theyare 1800 (=π) out of phase with the sampling data of the compositesignal DM of line k.

Non-standard NTSC signal are processed in the same way. The phases ofthe composite signals DB and DT of lines k+1 and k−1 are corrected byphase corrections Δb and Δt, respectively. The sampling data of thecomposite signals DT, DM, and DB of lines k−1, k, and k+1 are outputfrom the sampling phase conversion means 8 with their phases correctedto invert between lines.

FIGS. 8(a)-(c) are diagrams illustrating sampling phase conversion infurther detail. The clock signal with a frequency X of 27 MHz generatedby the clock generating means 2 is shown in FIG. 8(a); the input signalof line k−1 (dotted line in FIG. 7) is shown in FIG. 8(b); and thesignal of line k−1 after sampling phase conversion (solid line in FIG.7) is shown in FIG. 8(c).

The role of the sampling phase conversion means 8 is to output a digitalsignal identical in principle to a signal that would be obtained fromA/D conversion following a phase correction (phase shift) of the analogsignal input to the A/D conversion means 1. If the phase of the analogsignal were to be shifted, phase error extraction, control of an analogphase-shifting circuit, element-to-element variations, and otherproblems would have to be addressed. In this embodiment, the phase ofthe analog signal is not shifted before A/D conversion, but the samplingphase of the digital video signal obtained through A/D conversion on asingle free run clock is corrected according to phase error with respectto a reference value based on the phase information in the burst signalso as to establish the prescribed phase relationship.

In the actual sampling performed in the A/D conversion means 1, theinput signal shown in FIG. 8(b) (the dotted line in FIG. 7) is sampledon the rise of the clock pulses shown in FIG. 8(b) to obtain the sampledvalues represented by the white circles shown in FIG. 8(b).

The values of the phase-corrected signal (solid line in FIG. 7),represented by the black dots shown in FIG. 8(c), cannot be obtainedsimply by a temporal shift of the sampled values on the input signal(dotted line); it is necessary to change the magnitudes of the values.This is performed by the phase conversion filter 5 shown in FIG. 5. Thesampled values on the broken line shown in FIG. 7 (white circles shownin FIG. 8(b)) are combined to obtain values on the solid line shown inFIG. 7 (black-dots shown in FIG. 8(c)).

In the Y/C separation means 9, a C signal is extracted from thecomposite signals DB, DM, and DT of lines k+1, k, and k−1 in accordancewith the NTSC color subcarrier frequency fsc(NTSC), and the Y and Csignals are separated.

Operation when a PAL Composite Signal Is Input

When a PAL composite video signal is input to the input terminal 100,the following operations are performed. Since the PAL system has beenspecified by the broadcast system setting means 7, the sinewave ROM 15in the burst phase detecting means 3 outputs a reference signal with thePAL color subcarrier frequency fsc(PAL) to the phase comparison means12, and phase information p for a signal with the PAL color subcarrierfrequency fsc(PAL) is output from the NCO 14.

In a PAL composite signal, the color subcarrier phase changes by 270°(that is, −90°) at each line. The phase inverts by 180° (=90 ) atintervals of two lines. If the target line is line k, the colorsubcarrier phase of line k is inverse to the color subcarrier phase onlines k−2 and k+2. In the PAL system, the color subcarrier phase of theR-Y signal is inverted by 180° at each line.

If the one-line delay performed for an NTSC signal is replaced by atwo-line delay, the color subcarrier phase of the signals output fromthe delaying means inverts by 180° on alternate lines, and the colorsubcarrier phase of the R-Y signal has the same sign.

In the phase difference calculation means 4, the selection means 25selects the color subcarrier phase information p(k−2) for line k−2, twolines above line k on the screen, and the color subcarrier phaseinformation p(k+2) for line k+2, two lines below line k on the screen.The phase error calculation means 26 receives the phase informationp(k−2) and p(k+2) together with the color subcarrier phase informationp(k) for line k.

The phase error calculation means 26 is thus supplied with the phaseinformation p(k+2) output from the burst phase detecting means 3 asphase information for line k+2, the two-line-delayed phase informationp(k) output from delaying means 22 as phase information for line k, andthe four-line-delayed phase information p(k−2) output from delayingmeans 24 as phase information for line k−2.

In consideration of the phase inversion of π at intervals of two lines,the phase error calculation means 26 in the phase difference calculationmeans 4 calculates the phase error δb with respect to the phaseinformation p(k) for line k which is to be corrected in the signal ofline k+2 two lines below as follows,δb=p(k+2)−p(k)−πand calculates the phase error δt with respect to the phase informationp(k) for line k which is to be corrected in the signal of line k−2 twolines above as followsδt=p(k−2)−p(k)+πwhere −π and +π are both fixed phase values and −p(k)−π and −p(k)+π areequivalent to reference phases with respect to line k on lines k+2 andk−2, respectively. Phase errors δb and δt are obtained as phasedifferences between the phase information p(k+2) and p(k−2) of lines k+2and k−2 and the reference phase with respect to line k.

For a standard PAL input signal with phase inverted by 180° at intervalsof two lines, phase errors δb and δt are both zero. For a non-standardsignal, values equivalent to the phase difference are obtained as phaseerrors δb and δt.

The phase correction conversion means 27 in the phase differencecalculation means 4 obtains the change ω(PAL) in PAL color subcarrierphase per clock in accordance with the PAL color subcarrier frequencyfsc(PAL) as follows:ω(PAL)=2π×fsc(PAL)/Xand converts phase errors δb and δt to phase corrections Δb and Δt asfollows:Δb=δb/ω(PAL)Δt=δt/ω(PAL)

In the sampling phase conversion means 8, when the composite signal ofline k+2 (the second line below line k on the screen) is suppliedthrough delay compensation means 34 to phase conversion filter 36, thecomposite signal of line k input from the one-line delaying means 31 andthe composite signal of line k−2 (the second line above line k on thescreen) input from the one-line delaying means. 33 are selected by theselection means 35. The composite signal of line k is supplied to delaycompensation means 37, and the composite signal of line k+2 is suppliedto phase conversion filter 38.

The phase conversion filters 36 and 38 configured as shown in FIG. 5correct the phases of the composite signals of lines k+2 and k−2 inaccordance with phase corrections Δb and Δt, respectively. The compositesignal DT of line k−2 with its phase corrected by phase conversionfilter 38, the composite signal DM of line k with a compensating delayapplied by delay compensation means 37, and the composite signal DB ofline k+2 with its phase corrected by phase conversion filter 36 areoutput to the Y/C separation means 9.

The sampling data of the composite signal DT of line k−2 and thecomposite signal DB of line k+2 are corrected to be 180° (=π) out ofphase with the sampling data of the composite signal DM of line k.

Non-standard PAL signal are processed in the same way. The phases of thecomposite signals DB and DT of lines k+2 and k−2 are corrected by phasecorrections Δb and Δt, respectively. The sampling data of the compositesignals DT, DM, and DB of lines k−2, k, and k+2 are output from thesampling phase conversion means 8 with their phases corrected to invertbetween lines.

In the Y/C separation means 9, a C signal is extracted from thecomposite signals DB, DM, and DT of lines k+2, k, and k−2 in accordancewith the PAL color subcarrier frequency fsc (PAL), and the Y and Csignals are separated.

In the NTSC system, the phase difference calculation means 4 calculatesphase errors among the target line and the lines immediately above andbelow the target line in accordance with color subcarrier phaseinformation p, and outputs phase corrections Δb and Δt. In the PALsystem, the phase difference calculation means 4 calculates phase errorsamong the target line and-the lines two lines above and below the targetline in accordance with color subcarrier phase information p, andoutputs phase corrections Δb and Δt.

In the NTSC system, the sampling phase conversion means 8 corrects thephases of the composite signals of lines k−1 and k+1, one line above andone line below line k, by phase corrections Δb and Δt, and outputscomposite signals DT, DM, and DB for the three lines k−1, k, and k+1. Inthe PAL system, the sampling phase conversion means 8 corrects thephases of the composite signals of lines k−2 and k+2, two lines aboveand two lines below line k, and outputs composite signals DT, DM, and DBfor the three lines k−2, k, and k+2.

In the above calculation of phase errors δb and δt, π is added orsubtracted to take the inversion of phase between lines intoconsideration, but the value taken into consideration is not limited toπ. The line-to-line phase relationship in each television broadcastsystem should be considered, and the phase error should take the offsetinto consideration so that the difference in color subcarrier phasebetween lines becomes 180°.

If the phase error calculation means 26 in the phase differencecalculation means 4 obtains a phase error to be corrected from theline-to-line phase information so that Y/C separation can be performedon the assumption of a 180° inversion of the color subcarrier phasebetween lines, then the sampling phase conversion means 8 can correctthe phase for other television broadcast systems such as PAL-N, PAL-M,and NTSC-4.43, and these television broadcast systems can also be easilysupported. If the color subcarrier phase of the R-Y signal inverts onalternate lines, as in the PAL system, the one-line delay processingperformed for the NTSC system should be replaced by two-line delayprocessing.

For television broadcast systems and non-standard signals in which thecolor subcarrier phase relationship is not an inverse relationship, thephase error calculation means 26 in the phase difference calculationmeans 4, through the same calculation process as performed for the NTSCand PAL systems, can obtain phase error values that allow for offset sothat the difference in color subcarrier phase between lines becomes180°.

For example, if the color subcarrier phase changes by ph per line andthe color subcarrier phase of the R-Y signal does not invert, as in theNTSC system, a phase error is obtained from the phase information p(k)of line k and the phase information p(k+1) of line k+1, which can beeasily correlated. If the phase p(k+1) of the signal of line k+1 isp(k)+ph, the phase error δb to be corrected in the signal of line k+1 iscalculated asδb=p(k+1)−p(k)−πso that the difference in color subcarrier phase between lines becomes180° regardless of the value of ph. The phase error δb is calculated inthe same way as in the NTSC system. If the color subcarrier phase of theR-Y signal inverts on alternate lines, as in the PAL system, the phaseerror on line k+2 with respect to line k is calculated in the same way.

The phase error δb for a standard signal is ph−π, and the phase error δbfor non-standard signals is obtained as the value of the phase offset.For non-standard composite signals obtained from reproduction by a VTRor the like, the phase offset caused by phase decay is obtained as thecorrection through the phase error calculation. Accordingly,non-standard signals of any television broadcast system can besupported.

If a SECAM signal is input, the necessary processing differs from theprocessing for the NTSC or PAL system, and in general two-dimensionalY/C separation is not performed. If the line-to-line color subcarrierphase relationship is taken into consideration, however, Y/C separationcan be carried out by performing the sampling phase conversion describedabove.

According to the first embodiment, the phase difference calculationmeans 4 calculates a phase error between lines from the color subcarrierphase information of the composite signal, regardless of the televisionbroadcast system, and even from a non-standard signal; a phasecorrection is obtained such that the difference in color subcarrierphase between lines becomes 180°; the sampling phase of the compositesignal is corrected through sampling phase conversion; and then Y/Cseparation is performed. Accordingly, excellent two-dimensional Y/Cseparation can be performed, regardless of the line-to-line phaserelationship, even with a non-standard signal, and degradation ofpicture quality after Y/C separation can be prevented. While the phasesof the signals in lines above and below the current line are corrected,the signal of the current line is not converted, so the effect of phasecorrection on picture quality is small.

The phase conversion filters 36 and 38 in the first embodiment need notbe configured as linear phase filters having a group delay correspondingto the phase correction Δn received from the phase differencecalculation means 4 as shown in FIG. 5; they may be configured as shownin FIG. 9 or 10. The phase correction can also be carried out by a phaseconversion filter configured as shown in FIG. 9 or 10, and goodtwo-dimensional Y/C separation can still be performed regardless of theline-to-line phase relationship, even with a non-standard signal,preventing degradation of picture quality after Y/C separation as in thefirst embodiment described above.

The phase conversion filters 36 and 38 shown in FIG. 9 comprise aplurality of delaying means producing a predetermined delay and selectthe output of the delaying means producing a delay corresponding to thephase correction Δn. The phase conversion filters 36 and 38 comprisecorrection delaying means 46-1 to 46-N and a selection means 47. Each ofthe correction delaying means 46-1 to 46-N has a different delay withinthe range of the phase correction Δn and outputs the input compositesignal to the selection means 47 with the corresponding delay. Theselection means 47 selects a signal having a delay corresponding to thephase correction Δn from the outputs of the correction delaying means46-1 to 46-N.

The phase conversion filters 36 and 38 shown in FIG. 10 are filters thatobtain sampled data values corresponding to the shifted positions causedby the phase correction Δn through interpolation, and comprise acoefficient generating means 48 and an interpolation filter 49. Thecoefficient generating means 48 generates an interpolation filtercoefficient hi for obtaining sampling data at positions corresponding tothe phase correction Δn. The interpolation filter 49 performsinterpolation in accordance with the filter coefficient hi given by thecoefficient generating means 48, and obtains and outputs sampling datavalues corresponding to the shifted positions caused by the phasecorrection Δn. Therefore, the interpolation filter 49 outputs acomposite signal with the phase corrected by the phase correction Δn.

The clock generating means 2 of the first embodiment generates a clockwith a frequency X of 27 MHz, but a clock with any type of frequency hasthe same effect. Even if the clock generating means 2 of the firstembodiment generates, for example, a burst locked clock based on theburst signal in the composite signal, or a line locked clock based onthe horizontal sync signal in the composite signal, Y/C separation canbe carried out after phase correction through sampling phase conversionand the same effects as described above can be obtained.

The Y/C separation means 9 in the first embodiment was described aboveas a two-dimensional Y/C separation means using a line comb filter toprocess signals from three lines, but the same effect as in the firstembodiment above is produced when the comb filter processes signals fromtwo lines, the signal of the current line and a one-line-delayed signal,provided sampling phase conversion of the composite signal is performedin accordance with the line-to-line color subcarrier phase relationshipand a phase correction is carried out to establish the prescribedline-to-line color subcarrier phase relationship.

The burst phase detecting means 3 of the first embodiment detects theburst phase from the composite signal output from the A/D conversionmeans 1, but this is not a restriction. The burst signal may also beextracted in a feedback loop; provided the color subcarrier phase of thecomposite signal can be detected on each line, this produces the sameeffect as in the first embodiment above.

The timing signal generating means 6 of the first embodiment generates atiming signal hb that indicates a position in the burst signal intervalin the horizontal blanking interval, but the timing signal may begenerated at any position. The same effect is obtained, provided thecolor subcarrier phase can be detected in each position indicated by thetiming signal.

The first embodiment described above is configured as hardware, but thisconfiguration may be implemented as program-controlled softwareprocessing.

Second Embodiment

In the first embodiment described above, the line-to-line phase errorwas obtained from consideration of the line-to-line phase inversion ofπ. In a second embodiment, described below, a correction is obtained bycomparing phase information for a certain line with a fixed phase value.

FIG. 11 is a block diagram showing an example of the structure of avideo signal processing circuit according to the second embodiment ofthe invention. Elements identical to elements shown FIG. 1 are denotedby the same reference numerals. As shown in FIG. 11, the video signalprocessing circuit of the second embodiment comprises an A/D conversionmeans 1, a clock generating means 2, a burst phase detecting means 3, async separation means 5, a timing signal generating means 6 a, abroadcast system setting means 7, a Y/C separation means 9, a phasedifference calculation means 60, a sampling phase conversion means61,.an input terminal 100, and output terminals 101, 102.

The video signal processing circuit of the second embodiment differsfrom the video signal processing circuit of the first embodiment (seeFIG. 1) in that the phase difference calculation means 4 is replaced bythe phase difference calculation means 60, the timing signal generatingmeans 6 is replaced by the timing signal generating means 6 a, and thesampling phase conversion means 8 is replaced by the sampling phaseconversion means 61. The configuration and operation of the parts otherthan the timing signal generating means 6 a, phase differencecalculation means 60, and sampling phase conversion means 61 are thesame as in the first embodiment.

Timing Signal Generating Means 6 a

The timing signal generating means 6 a generates a timing signals basedon the sync signal supplied from the sync separation means 5, andoutputs the timing signals to the phase difference calculation means 60and sampling phase conversion means 61. The timing signals generatedhere are a timing signal hb which indicates a sampling position in theburst signal interval of the horizontal blanking interval in accordancewith the horizontal sync signal and a timing signal h1 which indicates aline number (line position) in the input composite signal, such as aper-frame line number (0 to 524 in the NTSC system or 0 to 624 in thePAL system).

Phase Difference Calculation Means 60

The phase difference calculation means 60 calculates a phase error froma reference phase (a fixed phase value predetermined by the lineposition) in accordance with color subcarrier phase information p inputfrom the NCO 14 (see FIG. 2) in the burst phase detecting means 3, withrespect to the target line and lines thereabove-and therebelow, andoutputs phase corrections Δ0 m, Δ0 b, and Δ0 t to the sampling phaseconversion means 61.

FIG. 12 is a block diagram showing an example of the structure of thephase difference calculation means 60. Elements identical to elements inthe phase difference calculation means 4 shown in FIG. 3 are denoted bythe same reference numerals. As shown in FIG. 12, the phase differencecalculation means 60 comprises delaying means 21, 22, 23, 24, aselection means 25, a phase error calculation means 62, and a phasecorrection conversion means 63.

The phase difference calculation means 60 of the second embodimentdiffers from the phase difference calculation means 4 of the firstembodiment in that the phase error calculation means 26 is replaced bythe phase error calculation means 62, and the phase correctionconversion means 27 is replaced by the phase correction conversion means63. The configuration and operation of the parts other than the phaseerror calculation means 62 and the phase correction conversion means 63are the same as in the phase difference calculation means 4 of the firstembodiment.

In the phase difference calculation means 60 shown in FIG. 12, the phaseerror calculation means 62 is supplied with phase information p from theburst phase detecting means 3 and two items of phase information p fromthe selection means 25, as well as timing signal h1 from the timingsignal generating means 6 a and the television broadcast systemspecification signal from the broadcast system setting means 7.

The phase error calculation means 62 obtains phase differences fromfixed reference phases based on timing signal hi indicating the phase ofthe input line signal, the selected television broadcast system, and theline number of the input signal, from phase information p for the threelines supplied from the burst phase detecting means 3 and selectionmeans 25, as phase errors δ0 m, δ0 b, and δ0 t to be corrected, andoutputs them to the phase correction conversion means 63.

The phase correction conversion means 63 converts phase errors δ0 m, δ0b, and δ0 t from the phase error calculation means 62 to phasecorrections Δ0 m, Δ0 b, and Δ0 t to be used for phase correction, andoutputs them to the sampling phase conversion means 61.

Since the phase information p indicates an angle, where one period ofthe color subcarrier corresponds to 2π, the conversion process performedby the phase correction conversion means 63 converts the phase errors δ0m, δ0 b, and δ0 t output from the phase error calculation means 62 tovalues representing time with reference to one period of the clock witha frequency X of 27 MHz, (time represented as a multiple of the periodof clock with frequency X). If the change ω expressed in colorsubcarrier phase angle per clock period is 2π×fsc/X, where fsc is thecolor subcarrier frequency, the phase corrections Δ0 m, Δ0 b, and Δ0 tobtained by conversion of the phase errors δ0 m, δ0 b, and δ0 t areexpressed as follows:Δ0m=δm/ωΔ0b=δb/ωΔ0t=δt/ωIf the phase errors δ0 m, δ0 b, and δ0 t range from −π to +π, the phasecorrections Δ0 m, Δ0 b, and Δ0 t take on values from −X/(2×fsc) toX/(2×fsc)

Sampling Phase Conversion Means 61

The sampling phase conversion means 61 obtains, for example, digitalcomposite signals for three lines (the target line and lines thereaboveand therebelow) from the AID conversion means 1 as the signals to beused for Y/C separation, corrects the phases of the composite signals ofthe three lines by phase corrections Δ0 m, Δ0 b, and Δ0 t obtained fromthe phase difference calculation means 60, and outputs thephase-corrected composite signals DT, DM, and DB for the three lines tothe Y/C separation means 9.

FIG. 13 is a block diagram showing an example of the structure of thesampling phase conversion means 61, denoting elements identical toelements of the sampling phase conversion means 8 in FIG. 4 by the samereference numerals. As shown in FIG. 13, the sampling phase conversionmeans 61 comprises one-line delaying means 30, 31, 32, 33, a delaycompensation means 34, a selection means 35, and phase conversionfilters 64, 65, 66.

The sampling phase conversion means 61 of the second embodiment differsfrom the sampling phase conversion means 8 (see FIG. 4) of the firstembodiment in that phase conversion filter 36 is replaced by phaseconversion filter 64, delay compensation means 37 is replaced by phaseconversion filter 65, and phase conversion filter 38 is replaced byphase conversion filter 66. The configuration and operation of the partsother than the phase conversion filters 64, 65, and 66 are the same asin the sampling phase conversion means 8 in the first embodiment. Thephase conversion filters 64, 65, and 66 are configured and operate inthe same way as the phase conversion filters 36 and 38 (see FIGS. 5, 9,and 10) of the first embodiment, for example.

In the sampling phase conversion means 61 shown in FIG. 13, phaseconversion filter 64 receives phase correction Δ0 b from the phasedifference calculation means 60, phase conversion filter 65 receivesphase correction Δ0 m from the phase difference calculation means 60,and phase conversion filter 66 receives phase correction Δ0 t from thephase difference calculation means 60.

Phase conversion filter 64 corrects the phase of the composite signalfrom delay compensation means 34 in accordance with phase correction Δ0b from the phase difference calculation means 60, and outputs the signalto the Y/C separation means 9 as composite signal DB. Phase conversionfilter 65 corrects the phase of the composite signal from the selectionmeans 35 in accordance with phase correction Δ0 m from the phasedifference calculation means 60, and outputs the signal to the Y/Cseparation means 9 as composite signal DM. Phase conversion filter 66corrects the phase of the composite signal from the selection means 35in accordance with phase correction Δ0 t from the phase differencecalculation means 60, and outputs the signal to the Y/C separation means9 as composite signal DT.

Phase corrections Δ0 m, Δ0 b, and Δ0 t are phase corrections withrespect to reference color subcarrier phases on the three lines. Thephase corrections have been converted to values based on the period ofthe clock with a frequency X of 27 MHz. The signals of the three linesinput to the phase conversion filters 64, 65, and 66 are delayed by Δ0m, Δ0 b, and Δ0 t, respectively, thereby converting the sampling phasesand correcting the phases.

Operation when an NTSC Composite Signal Is Input When an NTSC compositevideo signal is input to the input terminal 100, the followingoperations are performed. In an NTSC composite signal, the colorsubcarrier phase inverts by 180° (=π) on alternate lines. If the targetline is line k, the color subcarrier phase of line k is inverse to thecolor subcarrier phase on line k−1 one line above and line k+1 one linebelow.

In the phase difference calculation means 60, the selection means 25selects the color subcarrier phase information p(k−1) for line k−1, oneline above line k on the screen, and the color subcarrier phaseinformation p(k+1) for line k+1, one line below line k on the screen.The phase error calculation means 62 receives the phase informationp(k−1) and p(k+1) together with the color subcarrier phase informationp(k) for line k.

In the NTSC system, the color subcarrier phase inverts by 180° onalternate lines. If even-numbered lines (lines 0, 2, and so on) have aphase of 0°, odd-numbered lines (lines 1, 3, and so on) have a phase of180°. Taking this into consideration, the phase error calculation means62 in the phase difference calculation means 60 sets the comparisonreference phase value to 0° for even-numbered lines and to 180° forodd-numbered lines, switches the values at intervals of two lines inaccordance with the selected television broadcast system and the timingsignal h1 indicating the line number of the input signal, and calculatesphase differences between the color subcarrier phase information p(k−1),p(k), and p(k+1) of lines k−1, k, and k+1 and the reference phases asphase errors δ0 t, δ0 m, and δ0 b to be corrected on lines k−1, k, andk+1, respectively.

If line k is an odd-numbered line, the phase error δ0 m to be correctedfor the signal of line k is obtained as follows:δ0m=p(k)−πThe phase error δ0 b to be corrected for the signal of line k+1 one linebelow is obtained as follows:δ0b=p(k+1)−0The phase error δ0 t to be corrected for the signal of line k−1 one lineabove is obtained as follows:δ0t=p(k−1)−0The last terms −π, −0, and −0 correspond to fixed reference phasesdepending on the line position. Phase differences between the phaseinformation p(k−1), p(k), and p(k+1) of lines k−1, k, and k+1 and thefixed reference phases are obtained as phase errors δ0 t, δ0 m, and δ0b, respectively.

If line k is an even-numbered line, the phase error δ0 m to be correctedfor the signal of line k is obtained as follows:δ0m=p(k)−0The phase error δ0 b to be corrected for the signal of line k+1 one linebelow is obtained as follows:δ0b=p(k+1)−πThe phase error δ0 t to be corrected for the signal of line k−1 one lineabove is obtained as follows:δ0t=p(k−1)−πThe last terms −0, −π, and −π correspond to fixed reference phasesdepending on the line position. Phase differences between the phaseinformation p(k−1), p(k), and p(k+1) of lines k−1, k, and k+1 and thefixed reference phases are obtained as phase errors δ0 t, δ0 m, and δ0b, respectively.

For a standard NTSC input signal with a line-to-line phase inversion of180°, phase errors δ0 t, δ0 m, and δ0 b are all zero. For a non-standardsignal, values equivalent to phase offsets from the reference phases onthe individual lines are obtained as phase errors δ0 t, δ0 m, and δ0 b.

The phase correction conversion means 63 in the phase differencecalculation means 60 obtains the amount of change ω(NTSC) in NTSC colorsubcarrier phase per clock in accordance with the NTSC color subcarrierfrequency fsc(NTSC) as follows,ω(NTSC)=2π×fsc(NTSC)/Xand converts phase errors δ0 m, δ0 b, and δ0 t to phase corrections Δ0m, Δ0 b, and Δ0 t as follows:Δ0m=δ0m/ω(NTSC)Δ0b=δ0b/ω(NTSC)δ0t=δ0t/ω(NTSC)

In the sampling phase conversion means 61, when the composite signal ofline k+1 (the line immediately below line k on the screen) is suppliedthrough delay compensation means 34 to phase conversion filter 64, theselection means 35 selects the composite signal of line k suppliedthrough one-line delaying means 30 and the composite signal of line k−1(the line immediately above line k on the screen) supplied throughone-line delaying means 31. The composite signal of-line k is output tophase conversion filter 65, and the composite signal of line k−1 isoutput to phase conversion filter 66.

The phase conversion filters 64, 65, and 66 correct the phases of thecomposite signals of lines k+1, k, and k−1 in accordance with respectivephase corrections Δ0 b, Δ0 m, and Δ0 t. The composite signal DT of linek−1 with its phase corrected by phase conversion filter 66, thecomposite signal DM of line k with its phase corrected by phaseconversion filter 65, and the composite signal DB of line k +1 with itsphase corrected by phase conversion filter 64 are output to the Y/Cseparation means 9.

The sampling data of the composite signal DT of line k−1 and thecomposite signal DB of line k+1 are corrected so that they are 180° (=π)out of phase with the sampling data of the composite signal DM of linek.

Non-standard NTSC signals are processed in the same way. The phases ofthe composite signals of lines k+1, k, and k−1 are corrected by phasecorrections Δ0 b, Δ0 m, and Δ0 t, respectively. The sampling data of thecomposite signals DT, DM, and DB of lines k−1, k, and k+1 are outputfrom the sampling phase conversion means 61 with their phases correctedto invert between lines.

In the Y/C separation means 9, a C signal is extracted from thecomposite signals DB, DM, and DT of lines k+1, k, and k−1 in accordancewith the NTSC color subcarrier frequency fsc(NTSC), and the Y and Csignals are separated.

Operation when a PAL Composite Signal Is Input When a PAL compositevideo signal is input to the input terminal 100, the followingoperations are performed. In a PAL composite signal, the colorsubcarrier phase changes by 270° (that is, −90°) at each line. The phaseinverts by 180° (=π) at intervals of two lines. If the target line isline k, the color subcarrier phase of line k is inverse to the colorsubcarrier phase on line k−2 two lines above and line k+2 two linesbelow. In the PAL system, the color subcarrier phase of the R-Y signalis inverted by 180° at each line.

In the phase difference calculation means 60, the selection means 25selects the color subcarrier phase information p(k−2) for line k−2, twolines above line k on the screen, and the color subcarrier phaseinformation p(k+2) for line k+2, two lines below line k on the screen.The phase error calculation means 62 receives the phase informationp(k−2) and p(k+2) together with the color subcarrier phase informationp(k) for line k.

In the PAL system, the phase changes successively in a cycle of fourlines (changes in a four-line sequence). When the phases of the firstlines (lines 0, 4, and so on) are 0°, the phases of the second lines(lines 1, 5, and so on) are 270° (=3π/2), the phases of the third lines(lines 2, 6, and so on) are 180°, and the phases of the fourth lines(lines 3, 7, and so on) are 90° (=π/2). The color subcarrier phase ofthe R-Y signal inverts by 180° at each line. Taking this intoconsideration, the phase error calculation means 62 in the phasedifference calculation means 60 changes the value of the comparisonreference phase at intervals of four lines, in accordance with theselected television broadcast system and the timing signal h1 indicatingthe line number of the input signal, and calculates phase differencesbetween color subcarrier phase information p(k−2), p(k), and p(k+2) oflines k−2, k, and line k+2 with the reference phases as phase errors δ0t, δ0 m, and δ0 b to be corrected on lines k−2, k, and k+2,respectively.

If line k is the first line of the four-line sequence, the phase errorδ0 m to be corrected for the signal of line k is obtained as follows:δ0m=p(k)−0The phase error δ0 b to be corrected for the signal of line k+2 twolines below is obtained as follows:δ0b=p(k+2)−πThe phase error δ0 t to be corrected for the signal of line k−2 twolines above is obtained as follows:δ0t=p(k−2)−πThe last terms −0, −π, and −π correspond to the fixed reference phasesdepending on the line position. Phase differences between the phaseinformation p(k−2), p(k), and p(k+2) of lines k−2, k, and k+2 and thefixed reference phases are obtained as phase errors δ0 t, δ0 m, and δ0b, respectively.

If line k is the second line of the four-line sequence, the phase errorδ0 m to be corrected for the signal of line k is obtained as follows:δ0m=p(k)−3π/2The phase error δ0 b to be corrected for the signal of line k+2 twolines below is obtained as follows:δ0b=p(k+2)−π/2The phase error δ0 t to be corrected for the signal of line k−2 twolines above is obtained as follows:δ0t=p(k−2)−π/2The last terms −3π/2, −π/2, and −π/2 correspond to the fixed referencephases depending on the line position. Phase differences between thephase information p(k−2), p(k), and p(k+2) of lines k−2, k, and k+2 andthe fixed reference phases are obtained as phase errors δ0 t, δ0 m, andδ0 b, respectively.

If line k is the third line of the four-line sequence, the phase errorδ0 m to be corrected for the signal of line k is obtained as follows:δ0m=p(k)−πThe phase error δ0 b to be corrected for the signal of line k+2 twolines below is obtained as follows:δ0b=p(k+2)−0The phase error δ0 t to be corrected for the signal of line k−2 twolines above is obtained as follows:δ0t=p(k−2)−0The last terms −π, −0, and −0 correspond to the fixed reference phasesdepending on the line position. Phase differences between the phaseinformation p(k−2), p(k), and p(k+2) of lines k−2, k, and k+2 and thefixed reference phases are obtained as phase errors δ0 t, δ0 m, and δ0b, respectively.

If line k is the fourth line of the four-line sequence, the phase errorδ0 m to be corrected for the signal of line k is obtained as follows:δ0m=p(k)−π/2The phase error δ0 b to be corrected for the signal of line k+2 twolines below is obtained as follows:δ0b=p(k+2)−3π/2The phase error δ0 t to be corrected for the signal of line k−2 twolines above is obtained as follows:δ0t=p(k−2)−3π/2The last terms −π/2, −3π/2, and −3π/2 correspond to the fixed referencephases depending on the line position. Phase differences between thephase information p(k−2), p(k), and p(k+2) of lines k−2, k, and k+2 andthe fixed reference phases are obtained as phase errors δ0 t, δ0 m, andδ0 b, respectively.

For a standard PAL input signal with phase inverted by 180° at intervalsof two lines, phase errors 60 m, δ0 b, and δ0 t are all zero. For anon-standard signal, values equivalent to offsets from the referencephases of the individual lines are obtained as phase errors δ0 m, δ0 b,and δ0 t.

The phase correction conversion means 63 in the phase differencecalculation means 60 obtains the change ω(PAL) in PAL color subcarrierphase per clock in accordance with the PAL color subcarrier frequencyfsc (PAL) as follows:ω(PAL)=2π×fsc(PAL)/Xand converts phase errors δ0 m, δ0 b, and δ0 t to phase corrections Δ0m, Δ0 b, and Δ0 t as follows:Δ0m=δ0m/ω(PAL)Δ0b=δ0b/ω(PAL)Δ0t=δ0t/ω(PAL)

In the sampling phase conversion means 61, when the composite signal ofline k+2 (the second line below line k on the screen) is suppliedthrough delay compensation means 34 to phase conversion filter 36, thecomposite signal of line k input from the one-line delaying means 31 andthe composite signal of line k−2 (the second line above line k on thescreen) input from the one-line delaying means 33 are selected by theselection means 35. The composite signal of line k is supplied to phaseconversion filter 65, and the composite signal of line k−2 is suppliedto phase conversion filter 66.

The phase conversion filters 64, 65, and 66 in the sampling phaseconversion means 61 correct the phases of the composite signals of linesk+2, k, and k−2 in accordance with phase corrections Δ0 b, Δ0 m and Δ0t, respectively. The composite signal DT of line k−2 with its phasecorrected by phase conversion filter 66, the composite signal DM of linek with its phase corrected by phase conversion filter 65, and thecomposite signal DB of line k+2 with its phase corrected by phaseconversion filter 64 are output to the Y/C separation means 9.

The sampling data of the composite signal DT of line k−2 and thecomposite signal DB of line k+2 are corrected to be 180° (=π) out ofphase with the sampling data of the composite signal DM of line k.

Non-standard PAL signals are processed in the same way. The phases ofthe composite signals DB, DM, and DT of lines k+2, k, and k−2 arecorrected by phase corrections Δ0 b, Δ0 m, and Δ0 t, respectively. Thesampling data of the composite signals DT, DM, and DB of lines k−2, k,and k+2 are output from the sampling phase conversion means 61 withtheir phases corrected to invert between lines.

In the Y/C separation means 9, a C signal is extracted from thecomposite signals DB, DM, and DT of lines k+2, k, and k−2 in accordancewith the PAL color subcarrier frequency fsc (PAL), and the Y and Csignals are separated.

In the NTSC system, the phase difference calculation means 60 calculatesphase errors from the reference phases on the target line and the linesimmediately above and below the target line in accordance with colorsubcarrier phase information p, and outputs phase corrections Δ0 b, Δ0m, and Δ0 t. In the PAL system, the phase difference calculation means60 detects phase errors from the reference phases on the target line andthe lines two lines above and below the target line in accordance withcolor subcarrier phase information p, and outputs phase corrections Δ0b, Δ0 m, and Δ0 t.

In the NTSC system, the sampling phase conversion means 61 corrects thephases of the composite signals of lines k−1, k, and k+1 by phasecorrections Δ0 b, Δ0 m, and Δt, and outputs composite signals DT, DM,and DB for the three lines k−1, k, and k+1. In the PAL system, thesampling phase conversion means 61 corrects the phases of the compositesignals of lines k−2, k, and k+2, and outputs composite signals DT, DM,and DB for the three lines k−2, k, and k+2.

In the above calculation of phase errors δ0 m, δ0 b, and δ0 t, thereference phase values are set to 0° or 180°, but the reference phasevalues can be set to other values that represent the color subcarrierphase and the line-to-line phase relationship with respect to thesampling positions extracted for the corresponding lines, and that allowfor offset so that the difference in color subcarrier phase betweenlines becomes 180°.

If the phase error calculation means 62 in the phase differencecalculation means 60 obtains the phase error to be corrected from theline-to-line phase information and the reference phase so that Y/Cseparation can be performed on the assumption of a 180° inversion of thecolor subcarrier phase between lines, the sampling phase conversionmeans 61 can correct the phase for other television broadcast systemssuch as PAL-N, PAL-M, and NTSC-4.43, and these television broadcastsystems can also be easily supported.

For television broadcast systems and non-standard signals in which thecolor subcarrier phase relationship is not an inverse relationship, thephase error calculation means 62 in the phase difference calculationmeans 60, through the same calculation process as performed for the NTSCand PAL systems, can obtain phase error values that allow for offset sothat the difference in color subcarrier phase between lines becomes1800.

If a SECAM signal is input, the necessary processing differs from theprocessing for the NTSC or PAL system, and in general two-dimensionalY/C separation is not performed. If the line-to-line color subcarrierphase relationship is taken into consideration, however, Y/C separationcan be carried out by performing the sampling phase conversion describedabove.

According to the second embodiment, the phase difference calculationmeans 60 calculates phase errors from the reference phase values for theindividual lines from the color subcarrier phase information of thecomposite signals, regardless of the television broadcast system, andeven from a non-standard signal; a phase correction is obtained suchthat the difference in color subcarrier phase between lines becomes180°; the sampling phase of the composite signal is corrected throughsampling phase conversion; and then Y/C separation is performed.Accordingly, excellent two-dimensional Y/C separation can be performed,regardless of the line-to-line phase relationship, even with anon-standard signal, and degradation of picture quality after Y/Cseparation can be prevented. Since the phase in a line is compared witha fixed reference phase, the phase error calculation can be structuredas the subtraction of a fixed value, so the circuit can be configuredeasily.

The timing signal generating means 6 a of the second embodimentgenerates a timing signal hb which indicates a position in the burstsignal interval of the horizontal blanking interval and a timing signalh1 which indicates a line number in a frame, but the timing signal hbfor detecting the color subcarrier phase may be generated at anyposition. The same effect is obtained as in the second embodiment above,provided the color subcarrier phase is detected in each positionindicated by the timing signal. Timing signal hi, which indicates a linenumber in a frame, can be any timing signal that repeats according tothe change in the color subcarrier phase from line to line; the sameeffect is produced, provided the signal enables odd-numbered lines andeven-number lines to be discriminated in the NTSC system, and indicatesthe four-line sequence in the PAL system.

The second embodiment described above is configured as hardware, butthis configuration may be implemented as program-controlled softwareprocessing.

Third Embodiment

In the first and second embodiments described above, the phase of thevideo signal was corrected by the phase correction output from the phasedifference calculation means. In a third embodiment, described below,the phase of the sampling clock is corrected by the phase correctionoutput from the phase difference calculation means, thereby providingthe video signal with the phase relationship used in Y/C separation.

FIG. 14 is a block diagram showing an example of the structure of avideo signal processing circuit according to the third embodiment of theinvention, denoting elements identical to elements shown in FIG. 1 or 11by the same reference numerals. As shown in FIG. 14, the video signalprocessing circuit of the third embodiment comprises an A/D conversionmeans 1, a clock generating means 2, a burst phase detecting means 3, async separation means 5, a timing signal generating means 6 b, abroadcast system setting means 7, a Y/C separation means 9, a clockphase correction means 70, a phase difference calculation means 71, aline delay selection means 72, an input terminal 100, and outputterminals 101, 102.

The video signal processing circuit of the third embodiment differs fromthe video signal processing circuit of the first or second embodiment(see FIG. 1 or 11) in that the phase difference calculation means 4 or60 is replaced by the phase difference calculation means 71, the timingsignal generating means 6 or 6 a is replaced by the timing signalgenerating means 6 b, and the clock phase correction means 70 and linedelay selection means 72 are provided as a means equivalent to thesampling phase conversion means 8. The configuration and operation ofthe parts other than the timing signal generating means 6 b, clock phasecorrection means 70, phase difference calculation means 71, and linedelay selection means 72 are the same as in the first or secondembodiment described above.

Clock Phase Correction Means 70

The clock phase correction means 70 corrects the phase of a clockgenerated by the clock generating means 2 by imparting a delaycorresponding to a phase correction Δc supplied from the phasedifference calculation means 71 to a clock with a prescribed frequency Xfrom the clock generating means 2, and supplies the phase-correctedclock to the A/D conversion means 1, burst phase detecting means 3, syncseparation means 5, timing signal generating means 6 b, Y/C separationmeans 9, phase difference calculation means 71, and line delay selectionmeans 72.

Accordingly, the A/D conversion means 1, burst phase detecting means 3,sync separation means 5, timing signal generating means 6 b, Y/Cseparation means 9, phase difference calculation means 71, and linedelay selection means 72, operate on a clock with a phase corrected bythe clock phase correction means 70.

Timing Signal Generating Means 6b The timing signal generating means 6bgenerates a timing signal h1 based on the sync signal supplied from thesync separation means 5, and outputs the timing signal to the phasedifference calculation means 71. The timing signal hi indicates a linenumber (line position) in the input composite signal, such as aper-frame line number (0 to 524 in the NTSC system or 0 to 624 in thePAL system), in accordance with the horizontal sync signal.

Phase Difference Calculation Means 71 From the color subcarrier phaseinformation p input from the NCO 14 (see FIG. 2) in the burst phasedetecting means 3, the phase difference calculation means 71 calculatesthe phase error from a reference phase (a predetermined fixed phasevalue depending on the line position) for the target line, and outputsthe phase correction Δc to the clock phase correction means 70.

FIG. 15 is a block diagram showing an example of the structure of thephase difference calculation means 71. As shown in the drawing, thephase difference calculation means 71 comprises a phase errorcalculation means 73 and a phase correction conversion means 74.

In the phase difference calculation means 71 shown in FIG. 15, the phaseerror calculation means 73 is supplied with phase information p from theburst phase detecting means 3, the timing signal h1 from the timingsignal generating means 6 b, and the television broadcast systemspecification signal from the broadcast system setting means 7.

The phase error calculation means 73 obtains the phase differencebetween the phase of the input line signal, which is obtained from thephase information p of the target line supplied by the burst phasedetecting means 3, and the fixed reference phase based on the selectedtelevision broadcast system and the timing signal h1 indicating the linenumber of the input signal, and outputs the phase error δc to becorrected to the phase correction conversion means 74.

The phase correction conversion means 74 converts the phase error δcsupplied from the phase error calculation means 73 to a phase correctionΔc applicable for the purpose of phase correction, and outputs it to theclock phase correction means 70. The procedure for converting the phaseerror δc to the phase correction Δc is the same as the procedure forconverting the phase error δ0 m to the phase correction Δ0 m in thephase correction conversion means 63 (see FIG. 12) in the secondembodiment, and will not be described here in detail.

The A/D conversion means 1 samples the input composite signal on a clockwith its phase corrected by the clock phase correction means 70 inaccordance with the phase correction Δc, so that sampling data for aline in which the phase correction is Δc is sampled by the A/Dconversion means 1 as data corrected by phase correction Δc, andconsequently, a composite signal with its phase corrected by the phasecorrection Δc is supplied from the A/D conversion means 1 to the linedelay selection means 72.

As has been described above, the phase difference calculation means 71compares the burst signal phase information p of each line with thefixed reference phase specified for the line, and obtains the phaseerror δc (phase correction Δc). The clock phase correction means 70compares the sampling phase of the signal in each line with thereference phase of the line, obtains the phase error δc for the line,and corrects the sampling clock phase of the line by the phase error δc.That is, the phase of the clock (FIG. 16(a)) output from the clockgenerating means 2 in FIG. 14 is corrected, and the corrected clock(FIG. 16(b)) is generated. A/D conversion of the input signal (FIG.16(c)) is performed on the corrected clock (FIG. 16(b)). For NTSCsignals, the reference phase value changes at intervals of two lines,being 0° for even-numbered lines and 180° for odd-numbered lines.

Line Delay Selection Means 72

From among the digital composite signals sampled on the phase-correctedclock, the line delay selection means 72 obtains digital compositesignals for three lines, for example, from the A/D conversion means 1 asthe signals to be used for Y/C separation, and outputs phase-correctedcomposite signals DT, DM, and DB for the three lines to the Y/Cseparation means 9. In the third embodiment, the line delay selectionmeans 72 and clock phase correction means 70 form a sampling phaseconversion means. Accordingly, the phase of the sampling clock iscorrected in accordance with the phase error of the burst signal withreference to the reference value obtained from the phase information,and the sampling phase is corrected so that the video signal obtained byA/D conversion using the phase-corrected clock and the correspondingline-delayed video signals have the prescribed phase relationship.

FIG. 17 is a block diagram showing an example of the structure of theline delay selection means 72. As shown in the drawing, the line delayselection means 72 comprises one-line delaying means 75 a, 75 b, 75 c,and 75 d, a delay compensation means 76, and a selection means 77.

In the line delay selection means 72 shown in FIG. 17, the compositesignal, sampled on the phase-corrected clock, is supplied from the A/Dconversion means 1 to one-line delaying means 75 a and the delaycompensation means 76. The television broadcast system specificationsignal is supplied from the broadcast system setting means 7 to theselection means 77.

One-line delaying means 75 a delays the input composite signal by oneline and outputs the delayed signal to one-line delaying means 75 b andthe selection means 77. One-line delaying means 75 b delays thecomposite signal output from one-line delaying means 75 a by one moreline, and outputs the delayed signal to one-line delaying means 75 c andthe selection means 77. One-line delaying means 75 c delays thecomposite signal output from one-line delaying means 75 b by yet onemore line, and outputs the delayed signal to one-line delaying means 75d. One-line delaying means 75 d delays the composite signal output fromone-line delaying means 75 c by still another line, and outputs thedelayed signal to the selection means 77.

The delay compensation means 76 outputs the input composite signalobtained from the A/D conversion means 1 to the Y/C separation means 9as composite signal DB, with compensation for the delay of the signaloutput from-the selection means 77. The selection means 77 selects twosignals from the signals input from the one-line delaying means 75 a, 75b, and 75 d in accordance with the television broadcast system, on thebasis of the television broadcast system specified by the broadcastsystem setting means 7, and outputs these signals as composite signal DMand composite signal DT to the Y/C separation means 9.

Operation when an NTSC Composite Signal Is Input When an NTSC compositevideo signal is input to the input terminal 100, the followingoperations are performed. The color subcarrier phase of the NTSCcomposite signal inverts by 180° (=π) on alternate lines. If the targetline is line k, the color subcarrier phase of line k is inverted in linek−1 one line above and in line k+1 one line below.

In the NTSC system, the color subcarrier phase inverts by 180° onalternate lines. If even-numbered lines (lines 0, 2, and so on) have aphase of 0°, odd-numbered lines (lines 1, 3, and so on) have a phase of180°. Taking this into consideration, the phase error calculation means73 in the phase difference calculation means 71 sets the comparisonreference phase value to 0° for even-numbered lines and to 180° forodd-numbered lines, switches the values at intervals of two lines inaccordance with the selected television broadcast system and the timingsignal h1 indicating the line number of the input signal, and calculatesthe phase difference between the color subcarrier phase information p(k)of line k and the reference phase as phase error δc.

When a signal of an odd-numbered line is input, the phase error δc to becorrected is obtained as follows:δc=p−πWhen a signal of an even-numbered line is input, the phase error δc tobe corrected is obtained as follows:δc=p−0

For a standard NTSC input signal with a line-to-line phase inversion of180°, the phase error δc is zero. For a non-standard signal, a valueequivalent to a phase offset from the reference phase is obtained as thephase error δc.

The phase correction conversion means 74 in the phase differencecalculation means 71 obtains the amount of change ω(NTSC) in NTSC colorsubcarrier phase per clock in accordance with the NTSC color subcarrierfrequency fsc(NTSC) as follows,ω(NTSC)=2π×fsc(NTSC)/Xand converts the phase error δc to-the phase correction Δc as follows:Δc=δc/ω(NTSC)

In the NTSC system, the color subcarrier phase of line k is inverted online k−1 one line above and on line k+1 one line below. In the linedelay selection means 72, when the composite signal of line k+1 (oneline below line k, which is the target line on the screen) is input tothe delay compensation means 76, the selection means 77 selects thecomposite signal of line k input from one-line delaying means 75 a andthe composite signal of line k−1 (one line above line k on the screen)input from one-line delaying means 75 b.

The composite signal DT of line k−1 output from one-line delaying means75 b, composite signal DM of line k output from one-line delaying means75 a, and composite signal DB of line k+1 output from the delaycompensation means 76 are output to the Y/C separation means 9 ascomposite signals for three lines.

The composite signal of line k+1 has been sampled by the A/D conversionmeans 1 on a sampling clock with its phase corrected by the phasecorrection Δc(k+1) calculated from the color subcarrier phaseinformation p(k+1) of line k+1; the composite signal of line k has beensampled by the A/D conversion means 1 on a sampling clock with its phasecorrected by the phase correction Δc(k) calculated from the colorsubcarrier phase information p(k) of line k; the composite signal ofline k−1 has been sampled by the A/D conversion means 1 on a samplingclock with its phase corrected by the phase correction Δc(k−1)calculated from the color subcarrier phase information p(k−1) of linek−1.

Because the composite signal input to the line delay selection means 72has been sampled on a clock corrected by the phase correction Δc of therelevant line, the sampling data-of the composite signal DT of line k−1and the composite signal DB of line k+1 are corrected to be 180° (=π)out of phase with the sampling data of the composite signal DM of linek.

For non-standard NTSC signals as well, the sampling clock phases forlines k+1, k, and k−1 are corrected by phase corrections Δc(k+1), Δc(k),and Δc(k−1), respectively. The sampling data of the composite signalsDT, DM, and DB of lines k−1, k, and k+1 are output from the line delayselection means 72 with their phases corrected to invert between lines.

In the Y/C separation means 9, a C signal is extracted from thecomposite signals DB, DM, and DT of lines k+1, k, and k−1 in accordancewith the NTSC color subcarrier frequency fsc(NTSC), and the Y and Csignals are separated.

Operation when a PAL Composite Signal Is Input When a PAL compositevideo signal is input to the input terminal 100, the followingoperations are performed. In a PAL composite signal, the colorsubcarrier phase changes by 270° (that is, −90°) at each line. The phaseinverts by 180° (=π) at intervals of two lines. If the target line isline k, the color subcarrier phase of line k is inverse to the colorsubcarrier phase on line k−2 two lines above and line k+2 two linesbelow. In the PAL system, the color subcarrier phase of the R-Y signalis inverted by 180° at each line.

In the PAL system, the phase changes successively in a cycle of fourlines (changes in a four-line sequence). When the phases of the firstlines (lines 0, 4, and so on) are 0°, the phases of the second lines(lines 1, 5, and so on) are 270° (=3π/2), the phases of the third lines(lines 2, 6, and so on) are 180°, and the phases of the fourth lines(lines 3, 7, and so on) are 90° (=π/2). The color subcarrier phase ofthe R-Y signal inverts by 180° at each line. Taking this intoconsideration, the phase error calculation means 73 in the phasedifference calculation means 71 changes the value of the comparisonreference phase at intervals of four lines, in accordance with theselected television broadcast system and the timing signal h1 indicatingthe line number of the input signal, and calculates the phase differencebetween the color subcarrier phase information p(k) of line k and thereference phase as the phase error δc to be corrected.

If the input signal is on the first line of the four-line sequence, thephase error δc to be corrected is obtained as follows:δc=p−0If the input signal is on the second line of the four-line sequence, thephase error δc to be corrected is obtained as follows:δc=p−3π/2If the input signal is on the third line of the four-line sequence, thephase error δc to be corrected is obtained as follows:δc=p−πIf the input signal is on the fourth line of the four-line sequence, thephase error δc to be corrected is obtained as follows:δc=p−π/2

For a standard PAL input signal with phase inverted by 180° at intervalsof two lines, the phase error δc is zero. For a non-standard signal, avalue equivalent to the offset from the reference phase is obtained asthe phase error δc.

The phase correction conversion means 74 in the phase differencecalculation means 71 obtains the change ω(PAL) in PAL color subcarrierphase per clock in accordance with the PAL color subcarrier frequencyfsc (PAL) as follows:ω(PAL)=2π×fsc(PAL)/Xand converts the phase error δc to a phase correction Δc as follows:Δc=δc/ω(PAL)

In the PAL system, the color subcarrier phase of line k is inverse tothe color subcarrier phase on line k−2 two lines above and line k+2 twolines below. In the line delay selection means 72, when the compositesignal of line k+2 (the second line below the target line, or line k, onthe screen) is supplied to the delay compensation means 76, thecomposite signal of line k input from one-line delaying means 75 b andthe composite signal of line k−2 (the second line above line k on thescreen) input from one-line delaying means 75 d are selected by theselection means 77.

The composite signal DT of line k−2 output from one-line delaying means75 d, composite signal DM of line k output from one-line delaying means75 b, and composite signal DB of line k+2 output from the delaycompensation means 76 are output to the Y/C separation means 9 ascomposite signals for three lines.

The composite signal of line k+2 has been sampled in the A/D conversionmeans 1 on a sampling clock with its phase corrected by the phasecorrection Δc(k+2) calculated from the color subcarrier phaseinformation p(k+2) of line k +2; the composite signal of line k has beensampled in the A/D conversion means 1 on a sampling clock with its phasecorrected by the phase correction Δc(k) calculated from the colorsubcarrier phase information p,(k) of line k; and the composite signalof line k−2 has been sampled in the A/D conversion means 1 on a samplingclock with its phase corrected by the phase correction Δc(k−2)calculated from the color subcarrier phase information p(k−2) of linek−2.

Because the composite signal input to the line delay selection means 72has been sampled on a clock corrected by the phase correction Δc of therelevant line, the sampling data of the composite signal DT of line k−2and the composite signal DB of line k+2 are corrected to be 180° (=π)out of phase with the sampling data of the composite signal DM of linek.

For non-standard PAL signals as well, the phases of the sampling clocksfor lines k+2, k, and k−2 are corrected by phase corrections Δc(k+2),Δc(k) and Δc(k−2), respectively. The sampling data of the compositesignals DT, DM, and DB of lines k−2, k, and k+2 are output from the linedelay selection means 72 with their phases corrected to invert betweenlines.

In the Y/C separation means 9, a C signal is extracted from thecomposite signals DB, DM, and DT of lines k+2, k, and k−2 in accordancewith the PAL color subcarrier frequency fsc(PAL), and the Y and Csignals are separated.

In the above calculation of phase error δc, the reference phase valuesare set to 0° or 180°, but the reference phase values can be set toother values that represent the color subcarrier phase and theline-to-line phase relationship with respect to the sampling positionsextracted for the corresponding lines, and that allow for offset so thatthe difference in color subcarrier phase between lines becomes 180°.

If the phase error calculation means 73 in the phase differencecalculation means 71 obtains the phase error to be corrected from thephase information and the reference phase so that Y/C separation can beperformed on the assumption of a 180° inversion of the color subcarrierphase between lines, the clock phase correction means 70 can correct thephase for other television broadcast systems such as PAL-N, PAL-M, andNTSC-4.43, and these television broadcast systems can also be easilysupported.

If a SECAM signal is input, the necessary processing differs from theprocessing for the NTSC or PAL system, and in general two-dimensionalY/C separation is not performed. If the line-to-line color subcarrierphase relationship is taken into consideration, however, Y/C separationcan be carried out by correcting the clock phase as described above.

According to the third embodiment, the phase difference calculationmeans 71 calculates a phase error from the reference phase value, basedon the color subcarrier phase information of the burst signal,regardless of the television broadcast system, even with a non-standardsignal; a phase correction is obtained such that the difference in colorsubcarrier phase between lines becomes 1800; the clock phase iscorrected; and the data of the composite signal are sampled on thecorrected clock. Accordingly, Y/C separation can be based on aline-to-line color subcarrier phase difference of 180°, excellenttwo-dimensional Y/C separation can be performed, regardless of theline-to-line phase relationship, even with a non-standard signal, anddegradation of picture quality after Y/C separation can be prevented.

The timing signal generating means 6 b of the third embodiment generatesa timing signal h1 which indicates a line number in a frame, but thetiming signal h1 can be any timing signal that repeats according to thechange in the color subcarrier phase from line to line; the same effectis produced, provided the signal enables odd-numbered lines andeven-number lines to be discriminated in the NTSC system, and indicatesthe four-line sequence in the PAL system.

The phase difference calculation means 71 of the third embodimentobtains a phase correction by calculating the phase difference betweenthe phase of the input line signal and a reference phase, but the phaseerror to be corrected can be obtained by calculating a phase differencewith respect to the phase information at a position on a certain line,using delaying means as in the phase difference calculation means 4 inthe first embodiment. The same effect is produced by obtaining a phasecorrection such that the difference in color subcarrier phase betweenlines becomes 180°, and by correcting the clock phase accordingly.

The third embodiment described above is configured as hardware, but thisconfiguration may be implemented as program-controlled softwareprocessing.

Fourth Embodiment

In the first to third embodiments described above, a separate burstphase detecting means 3 is provided to detect color subcarrier phaseinformation. In the fourth embodiment, phase information is generated inthe phase detection process that generates a color subcarrier referencesignal for use in color demodulation to obtain R-Y and B-Y colordifference signals from the C signal.

FIG. 18 is a block diagram showing an example of the structure of avideo signal processing circuit according to the fourth embodiment ofthe invention, denoting elements identical to elements shown in FIG. 1by the same reference numerals. As shown in FIG. 18, the video signalprocessing circuit according to the fourth embodiment comprises an A/Dconversion means 1, a clock generating means 2, a phase differencecalculation means 4, a sync separation means 5, a timing signalgenerating means 6, a broadcast system setting means 7, a sampling phaseconversion means 8, a Y/C separation means 9, a burst signal phasedetecting means 10, an input terminal 100, output terminals 103, 104,105, and a color demodulating means 110.

As shown in the drawing, the video signal processing circuit in thefourth embodiment differs from the video signal processing circuit inthe first embodiment (see FIG. 1) in using a burst signal phasedetecting means 10 different from the burst phase detecting means 3 inFIG. 1, and having an additional color demodulating means 110. Theconfiguration and operation of the parts other than the colordemodulating means 110 and burst signal phase detecting means 10 are theas described above in the first embodiment.

Burst Signal Phase Detecting Means 10 Like the burst phase detectingmeans 3 shown in FIG. 1, the burst signal phase detecting means 10detects a burst signal in a composite signal received from the A/Dconversion means 1 (detects the burst phase of the composite signal) byusing a color subcarrier reference signal, and outputs color subcarrierphase information p to the phase difference calculation means 4. Inaddition, the burst signal phase detecting means 10 generates a colorsubcarrier reference signal for color demodulation with frequency fscfor obtaining the R-Y and B-Y color difference signals from the C signalin accordance with the color subcarrier phase information p, and outputsthis fsc signal to the color demodulating means 110.

FIG. 19 is a block diagram showing an example of the structure of theburst signal phase detecting means 10, denoting elements identical toelements of the burst phase detecting means 3 in FIG. 2 by the samereference numerals. As shown in FIG. 19, the burst signal phasedetecting means 10 comprises a burst signal extraction means 11, a phasecomparison means 12, a loop filter 13, an NCO 14, and a sinewave ROM 15.

The burst signal phase detecting means 10 in the fourth embodimentdiffers from the burst phase detecting means 3 in the first embodiment(see FIG. 2) in that the reference signal with color subcarrierfrequency fsc generated by the sinewave ROM 15 is output to the colordemodulating means 110 as a color subcarrier reference signal for colordemodulation.

Color Demodulating Means 110

The color demodulating means 110 color-demodulates the R-Y and B-Y colordifference signals by multiplying the C signal extracted by the Y/Cseparation means 9 by the color subcarrier reference signal withfrequency fsc received from the burst signal phase detecting means 10 inaccordance with the television broadcast system specified by thebroadcast system setting means 7, and outputs the R-Y signal to outputterminal 104 and the B-Y signal to output terminal 105.

In the digital television studio encoding parameters defined by CCIR,the sampling frequency of the Y signal is 13.5 MHz, and the samplingfrequency of the R-Y and B-Y signals is 6.75 MHz. The sampling frequencyof the Y signal output from the Y/C separation means 9 and the R-Y andB-Y signals output from the color demodulating means 110 equals thefrequency of the clock with frequency X of 27 MHz generated by the clockgenerating means 2. The sampling frequency of the Y signal output fromthe Y/C separation means 9 is twice as high as the CCIR-defined samplingfrequency, and the sampling frequency of the R-Y and B-Y signals outputfrom the color demodulating means 110 is four times as high as theCCIR-defined sampling frequency. Accordingly, the outputs of the Y/Cseparation means 9 and color demodulating means 110 can be easilyconverted to a signal conforming to digital television studio encodingparameters.

According to the fourth embodiment, the phase difference calculationmeans calculates a phase error from the color subcarrier phaseinformation in a composite signal for any of a plurality of televisionbroadcast systems or for a non-standard signal; a phase correction isobtained to provide a line-to-line color subcarrier phase difference of180°; and Y/C separation is carried out after the sampling phase of thecomposite signal is corrected by sampling phase conversion. Accordingly,excellent two-dimensional Y/C separation is carried out, regardless ofthe line-to-line phase relationship, even with a non-standard signal,and degradation of picture quality after Y/C separation can beprevented. The color subcarrier phase information is obtained from theburst signal phase detection means generating a color reference signalfor color demodulation, so that excellent Y/C separation is carried out,and degradation of picture quality after Y/C separation is prevented,with no great increase in the size of the circuit.

In the fourth embodiment described above, the burst phase detectingmeans 3 of the first embodiment is replaced by the burst signal phasedetecting means 10, and the color demodulating means 110 is added, butthe same effect is obtainable by replacing the burst phase detectingmeans 3 of the second or third embodiment by the burst signal phasedetecting means 10 and adding the color demodulating means 110.

Fifth Embodiment

The Y/C separation means in the first to fourth embodiments performstwo-dimensional Y/C separation by utilizing a line comb filter. In afifth embodiment, a frame comb filter utilizing the frame-periodic colorsubcarrier phase relationship is used to carry out three-dimensional Y/Cseparation. For three-dimensional Y/C separation, the extension intothree dimensions is made by replacing the delaying means that applydelays of one line in the first to fourth embodiments with framedelaying means that apply delays of one frame, in units of fields, forexample. Excellent three-dimensional Y/C separation can then beperformed regardless of the frame-to-frame phase relationship, even witha non-standard signal, as in the first to fourth embodiments.

FIG. 20 is a block diagram showing an example of the structure of avideo signal processing circuit according to the fifth embodiment of theinvention, denoting elements identical to elements shown in FIG. 1 bythe same reference numerals. As shown in FIG. 20, the video signalprocessing circuit according to the fifth embodiment comprises an A/Dconversion means 1, a clock generating means 2, a burst phase detectingmeans 3, a sync separation means 5, a timing signal generating means 6c, a broadcast system setting means 7, a phase difference calculationmeans 81, a frame sampling phase conversion means 82, a Y/C separationmeans 83, an input terminal 100, and output terminals 101, 102.

The video signal processing circuit according to the fifth embodimentdiffers from the video signal processing circuit according to the firstembodiment (see FIG. 1) in that the phase difference calculation means 4is replaced by the phase difference calculation means 81, the timingsignal generating means 6 is replaced by the timing signal generatingmeans 6 c, the sampling phase conversion means 8 is replaced by theframe sampling phase conversion means 82, and the Y/C separation means 9is replaced by the Y/C separation means 83. The configuration andoperation of the parts other than the timing signal generating means 6c, phase difference calculation means 81, frame sampling phaseconversion means 82, and Y/C separation means 83 are the same as in thefirst embodiment.

Timing Signal Generating Means 6 c

The timing signal generating means 6 c generates a timing signal basedon the sync signals output from the sync separation means 5, and outputsthe signal to the phase difference calculation means 81 and framesampling phase conversion means 82. In this embodiment, it generates atiming signal vb, based on the horizontal and vertical sync signals, forcreating a one-frame (two-field) signal delay.

Phase Difference Calculation Means 81

The phase difference calculation means 81 detects the frame-to-framephase difference from the color subcarrier phase information p, andoutputs a phase correction Δf to the frame sampling phase conversionmeans 82.

FIG. 21 is a block diagram showing an example of the structure of thephase difference calculation means 81. As shown in the drawing, thephase difference calculation means 81 comprises a one-frame delayingmeans 84, a phase error calculation means 85, and a phase correctionconversion means 86.

In the phase difference calculation means 81 shown in FIG. 21, the phaseinformation p from the burst phase detecting means 3 is supplied to theone-frame delaying means 84 and phase error calculation means 85. Thetiming signal from the timing signal generating means 6 c is supplied tothe one-frame delaying means 84. The television broadcast systemspecification signal from the broadcast system setting means 7 issupplied to the phase correction conversion means 86.

The one-frame delaying means 84 outputs the phase information p to thephase error calculation means 85 with a delay of one frame (two fields)in accordance with the timing signal vb.

From the phase information p output from the burst phase detecting means3 and the one-frame-delayed phase information p output from theone-frame delaying means 84, the phase error calculation means 85obtains a phase error δf to be corrected between frames, and outputs itto the phase correction conversion means 86.

The phase correction conversion means 86 converts the phase error δfsupplied from the phase error calculation means 85 to a phase correctionΔf for correcting the phase, and outputs it to the frame sampling phaseconversion means 82.

Since the phase information p indicates an angle, where one period ofthe color subcarrier corresponds to 2π, the conversion process performedby the phase correction conversion means 86 converts the phase error δfoutput from the phase error calculation means 85 to a value representingtime with reference to one period of the clock with a frequency X of 27MHz, (time represented as a multiple of the period of the clock withfrequency X). If the change ω expressed in terms of color subcarrierphase angle per clock period is 2π×fsc/X, where fsc is the colorsubcarrier frequency, the phase correction Δf obtained by conversion ofthe phase error δf is expressed as follows:Δf=δf/ωIf the phase error δf ranges from −π to +π, the phase correction Δftakes on values from −X/(2×fsc) to X/(2×fsc)

Frame Sampling Phase Conversion Means 82

A one-frame-delayed version of the digital composite signal output fromthe AID conversion means 1 is obtained in the frame sampling phaseconversion means 82, in order to obtain the composite signal of thecurrent field and the composite signal of the same field with a delay ofone frame (the composite signal of the target line in the current fieldand the composite signal of the same line in the immediately precedingframe) so that these can be used for Y/C separation. The frame samplingphase conversion means 82 corrects the phase of the one-frame-delayedcomposite signal by the phase correction Δf received from the phasedifference calculation means 81, and outputs both signals to the Y/Cseparation means 83.

FIG. 22 is a block diagram showing an example of the structure of theframe sampling phase conversion means 82. As shown in the drawing, theframe sampling phase conversion means 82 comprises a one-frame delayingmeans 87, a delay compensation means 88, and a phase conversion means89. The phase conversion means 89 has the same configuration andoperates in the same way as the phase conversion filter of the firstembodiment (see FIG. 5, 9, or 10), for example.

In the frame sampling phase conversion means 82 shown in FIG. 22, thecomposite signal output from the A/D conversion means 1 is input to theone-frame delaying means 87 and delay compensation means 88. The timingsignal vb output from the timing signal generating means 6 c is input tothe one-frame delaying means 87. The phase correction Δf output from thephase difference calculation means 81 is input to the phase conversionmeans 89.

The one-frame delaying means 87 delays the input composite signal by oneframe in accordance with the timing signal vb, and outputs the delayedsignal to the phase conversion means 89.

The delay compensation means 88 outputs the composite signal from theA/D conversion means 1 as composite signal DO to the Y/C separationmeans 83, with compensation for the signal delay of the other compositesignal output from the phase conversion means-89.

The phase conversion means 89 corrects the phase of the composite signaloutput from the one-frame delaying means 87 in accordance with the phasecorrection Δf given by the phase difference calculation means 81, andoutputs the corrected signal as composite signal D1 to the Y/Cseparation means 83.

The phase correction Δf is a phase correction of the signal of theimmediately preceding frame with respect to the color subcarrier phasein the current field. The phase correction has been converted to a valuebased on the period of the clock with a frequency X of 27 MHz. Thesignal corresponding to the signal of the immediately preceding frameinput to the phase conversion means 89 is delayed by Δf, therebyconverting the sampling phase and correcting the phase.

Y/C Separation Means 83

The Y/C separation means 83 is a three-dimensional Y/C separation meansutilizing a frame comb filter. Through three-dimensional Y/C separation,it extracts a C signal. from the composite signal D0 of the currentfield and the composite signal D1 of the same field of the immediatelypreceding frame input from the frame sampling phase conversion means 82in accordance with the color subcarrier frequency fsc of the televisionbroadcast system specified by the broadcast system setting means 7,separates the Y and C signals, and outputs the C signal to outputterminal 101 and the Y signal to output terminal 102.

FIG. 23 is a block diagram showing an example of the structure of theY/C separation means 83, which performs three-dimensional Y/Cseparation. As shown in the drawing, the Y/C separation means 83comprises a subtractor 90, a bandpass filter (BPF) 91, and anothersubtractor 92.

In the Y/C separation means 83 shown in FIG. 23, the composite signal D0of the current field from the frame sampling phase conversion means 82is input to the subtractors 90 and 92. The composite signal D1 of thesame field output with a delay of one frame from the frame samplingphase conversion means 82 is input to subtractor 90. The televisionbroadcast system specification signal output from the broadcast systemsetting means 7 is input to the BPF 91.

Subtractor 90 extracts the C signal by subtracting the one-frame-delayedcomposite signal D1 from the current-field composite signal D0, andoutputs the C signal to the BPF 91. Because the color subcarrier phaseinverts between identical lines in adjacent frames, the C signal can beextracted completely through the process performed by subtractor 90,provided the composite signal has a strong frame-to-frame correlation.

The BPF 91 outputs the signal supplied from subtractor 90 to outputterminal 102 (see FIG. 20) and subtractor 92, removing unnecessarycomponents outside the frequency band of the C signal. The BPF 91 usedhere is a BPF corresponding to the color subcarrier frequency fsc of thespecified television broadcast system, in accordance with the televisionbroadcast system specification signal from the broadcast system settingmeans 7.

Subtractor 92 separates a Y signal by subtracting the C signal given bythe BPF 91 from the input composite signal D0 of the current field, andoutputs the Y signal to output terminal 101 (see FIG. 20).

Operation when an NTSC Composite Signal Is Input When an NTSC compositevideo signal is input to the input terminal 100, the followingoperations are performed. The color subcarrier phase of the NTSCcomposite signal inverts by 180° (=π) in alternate frames. The colorsubcarrier phase in a given line in the current frame (frame j) isinverted on the same line in the immediately preceding frame (framej−1). The Y/C separation means 83 separates the Y and C signals bythree-dimensional Y/C separation, exploiting the fact that the colorsubcarrier phase inverts in alternate frames.

In the phase difference calculation means 81, color subcarrier phaseinformation p(j, k) of the target line (line k) in frame j and colorsubcarrier phase information p(j−1, k) of the same line k in frame j−1are supplied to the phase error calculation means 85 as color subcarrierphase information.

The phase error calculation means 85 is supplied with the phaseinformation p(j, k) from the burst phase detecting means 3,corresponding to the phase information of line k (the target line) inframe j, and the one-frame-delayed phase information p(j−1, k) from theone-frame delaying means 84, corresponding to the phase information ofline k in frame j−1 (the same line in the field two fields before).

In consideration of the frame-to-frame phase inversion of π, the phaseerror calculation means 85 in the phase difference calculation means 81calculates the phase error δf, with respect to the signal for line k inframe j, which is to be-corrected in the signal of line k in frame j−1one frame before as follows,δf=p(j−1, k)−p(j, k)+πwhere +π is a fixed phase value, and −p(j, k)+π is equivalent to areference phase with respect to line k in frame j. A phase error δf isobtained as a phase difference between the phase information p(j−1, k)of line k in frame j−1 and the reference phase with respect to thetarget line.

For a standard NTSC input signal with a frame-to-frame phase inversionof 180°, the phase error δf is zero. For a non-standard signal, a valueequivalent to the phase offset is obtained as the phase error δf.

The phase correction conversion means 86 in the phase differencecalculation means 81 obtains the amount of change ω(NTSC) in NTSC colorsubcarrier phase per clock in accordance with the NTSC color subcarrierfrequency fsc(NTSC) as follows,ω(NTSC=π×fsc(NTSC)/Xand converts the phase error δf to a phase correction Δf as follows:Δf=δf/ω(NTSC)

In the frame sampling phase conversion means 82, when the compositesignal of line k in frame j is compensated to allow for the delay by thedelay compensation means 88, the composite signal of line k in frame j−1delayed by one frame by the one-frame delaying means 87 is input to thephase conversion means 89.

The phase conversion means 89 corrects the phase of the composite signalof line k in frame j−1 in accordance with the phase correction Δf. Thecomposite signal D1 of frame j−1 with its phase corrected by the phaseconversion means 89 and the composite signal D0 of frame j with acompensating delay applied by the delay compensation means 88 are outputto the Y/C separation means 9.

The data of the composite signal D1 of frame j−1 are corrected so thatthey are 180° (=π) out of phase with the sampling data of the compositesignal D0 of frame j.

Non-standard NTSC signals are processed in the same way. The phases ofthe composite signal D0 of frame j and the composite signal D1 of framej−1 one frame before are corrected by the phase correction Δf. Thesampling data of the composite signals D1 and D0 are output from theframe sampling phase conversion means 82 with their phases corrected toinvert between frames.

In the Y/C separation means 83, a C signal is extracted from thecomposite signal D0 of frame j and the composite signal D1 of frame j−1in accordance with the NTSC color subcarrier frequency fsc(NTSC), andthe Y and C signals are separated.

Operation when a PAL Composite Signal Is Input When a PAL compositevideo signal is input to the input terminal 100, the followingoperations are performed. In a PAL composite signal, the colorsubcarrier phase changes by 270° per frame. The phase inverts by 180°(=π) at intervals of two frames. If the current frame is frame j, thereis a phase offset of 3π/2 between the color subcarrier phase of frame jand the color subcarrier phase of frame j−1 one frame before. Frame jand frame j−2 two frames before have opposite color subcarrier phases.The Y/C separation means 83 exploits the correlatedness of frames, andseparates the C and Y signals through three-dimensional Y/C separationtaking the frame-to-frame color subcarrier phase inversion of 180° intoconsideration.

In the PAL system, the color subcarrier of the current frame inverts by180° in the second preceding frame, but these two frames will generallyhave a weak signal correlation. A weak frame correlation will adverselyaffect three-dimensional Y/C separation, and good Y/C separation cannotbe performed. Accordingly, it is inadvisable to use the current frameand the second preceding frame for three-dimensional Y/C separation.

In the PAL system, the phase difference calculation means 81 obtains aphase correction for correcting the phases to invert by 180° betweenframes, allowing for frame-to-frame phase error between the currentframe and the immediately preceding frame, as in the NTSC system.

As in the NTSC system, the phase error calculation means 85 in the phasedifference calculation means 81 calculates phase error δf, with respectto the signal for line k in frame j, which is to be corrected in thesignal of line k in frame j−1 one frame before, from color subcarrierphase information p(j, k) of the target line, which is line k in framej, and color subcarrier phase information p(j−1, k) of line k in framej−1, as followsδf=p(j−1)−p(j)+π

For a standard PAL signal input with a frame-to-frame phase shift of270°,p(j−1, k)=p(j, k)+3π/2Thereforeδf=(3π/2)+π=2π+π/2That isδf=π/2Accordingly, a signal with a phase of 0° (corresponding to a phase of270° in the current field) is corrected to a phase of 90°. For anon-standard signal, the phase error δf is obtained by adding a valueequivalent to the phase offset to π/2.

The phase correction conversion means 86 in the phase differencecalculation means 81 obtains the change ω(PAL) in PAL color subcarrierphase per clock in accordance with the PAL color subcarrier frequencyfsc(PAL) as follows:ω(PAL)=2π×fsc(PAL)Xand converts phase error δf to a phase correction Δf as follows:Δf=δf/ω(PAL)

In the frame sampling phase conversion means 82, the phase of compositesignal D1 of frame j−1 is corrected by the phase correction Δf so thatthe sampling data of the composite signal D1 of frame j−1 and thecomposite signal D0 of frame j become 180° (=π) out of phase, as in theNTSC system.

Non-standard PAL signals are processed in the same way. Since the phasecorrection Δf includes a value equivalent to the phase offset, the phaseis corrected by the phase correction Δf between frames, and the samplingdata of the composite signal D0 of frame j and the composite signal D1of frame j−1 one frame before are output from the frame sampling phaseconversion means 82 with their phases corrected to invert betweenframes.

In the Y/C separation means 83, a C signal is extracted from thecomposite signals D0 and D1 of frames j and j−1 in accordance with thePAL color subcarrier frequency fsc(PAL), and the Y and C signals areseparated.

In the above calculation of phase error δf, π is added to take theinversion of phase between frames into consideration, but the valuetaken into consideration is not limited to π. The frame-to-frame phaserelationship in each television broadcast system should be considered,and the phase error should take the offset into consideration so thatthe difference in color subcarrier phase becomes 180°.

If the phase error calculation means 85 in the phase differencecalculation means 81 obtains a phase error to be corrected from theframe-to-frame phase information so that Y/C separation can be performedon the assumption of a 180° inversion of the color subcarrier phasebetween frames, the frame sampling phase conversion means 82 can correctthe phase for other television broadcast systems, and these televisionbroadcast systems can also be easily supported.

According to the fifth embodiment, the phase difference calculationmeans 81 calculates a phase error between frames from the colorsubcarrier phase information of the composite signal, regardless of thetelevision broadcast system, and even from a non-standard signal; aphase correction is obtained such that the difference in colorsubcarrier phase between frames becomes 180°; the sampling phase of thecomposite signal is corrected through sampling phase conversion; andthen Y/C separation is performed. Accordingly, excellentthree-dimensional Y/C separation can be performed, regardless of theframe-to-frame phase relationship, even with a non-standard signal, anddegradation of picture quality after Y/C separation can be prevented.

The phase difference calculation means 81 in the fifth embodimentdescribed above obtains a phase correction by comparing the colorsubcarrier phase between frames, but the phase difference calculationmeans 81 may obtain a phase correction by comparing the color subcarrierphase with a fixed phase value as in the second embodiment.

The phase difference calculation means 81 of the fifth embodiment can beconfigured as shown in FIG. 24. In that case, the frame sampling phaseconversion means 82 can be configured as shown in FIG. 25.

The phase difference calculation means 81 shown in FIG. 24 comprises aone-frame delaying means 84, a phase error calculation means 93, and aphase correction conversion means 94. In FIG. 24, elements identical toelements of the phase difference calculation means 81 in FIG. 21 aredenoted by the same reference numerals. The phase error calculationmeans 93 specifies a comparison reference phase value based on a changein color subcarrier phase between frames, switches the value inaccordance with the specified television broadcast system and a timingsignal v1 from the timing signal generating means 6 c, compares both thephase information p of the current field and phase information p of thesame field of the immediately preceding frame output from the one-framedelaying means 84 with the reference phase value, calculates phasedifferences, and obtains the phase error δf0 to be corrected in thesignal of the current field and the phase error δf1 to be corrected inthe signal of the immediately preceding frame. In the phase correctionconversion means 94, the phase errors δf0 and δf1 output from the phaseerror calculation means 93 are converted to phase corrections Δf0 andΔf1 for correcting the phases.

The frame sampling phase conversion means 82 shown in FIG. 25 comprisesa one-frame delaying means 87 and phase conversion means 96, 96. In FIG.25, elements identical to elements of the frame sampling phaseconversion means 82 in FIG. 22 are denoted by the same referencenumerals. The phase conversion means 95 corrects the phase of thecomposite signal of the current field by applying a delay equal to phasecorrection Δf0. The phase conversion means 96 corrects the phase of thecomposite signal in the field one frame before the current field byapplying a delay equal to phase correction Δf1.

In the fifth embodiment described above, the phase of the video signalis corrected-by a phase correction output from the phase differencecalculation means 81, but if the phase of the sampling clock used forsampling is corrected as in the third embodiment, a phase relationshipuseful in three-dimensional Y/C separation can be established, and thesame effect is produced.

Sixth Embodiment

In the fifth embodiment, a separate burst phase detecting means 3 isprovided to detect color subcarrier phase information. In a sixthembodiment, as in the fourth embodiment, the phase information isgenerated by the burst signal phase detecting means 10 that generatesthe color subcarrier reference signal used in color demodulation toobtain the R-Y and B-Y signals from the chrominance signal.

FIG. 26 is a block diagram showing an example of the structure of avideo signal processing circuit according to the sixth embodiment of theinvention, denoting elements identical to elements shown in FIG. 18 or20 by the same reference numerals. As shown in FIG. 26, the video signalprocessing circuit comprises an A/D conversion means 1, a clockgenerating means 2, a sync separation means 5, a timing signalgenerating means 6 c, a broadcast system setting means 7, a burst signalphase detecting means 10, a phase difference calculation means 81, aframe sampling phase conversion means 82, a Y/C separation means 83, aninput terminal 100, output terminals 103, 104, 105, and a colordemodulating means 110.

The video signal processing circuit of the sixth embodiment differs fromthe video signal processing circuit of the fourth embodiment (see FIG.18) in that the phase difference calculation means 4 is replaced by thephase difference calculation means 81, the timing signal generatingmeans 6 is replaced by the timing signal generating means 6 c, thesampling phase conversion means 8 is replaced by the frame samplingphase conversion means 82, and the Y/C separation means 9 is replaced bythe Y/C separation means 83.

The video signal processing circuit of the sixth embodiment differs fromthe video signal processing circuit of the fifth embodiment (see FIG.20) in that the color demodulating means 110 is provided, and the burstphase detecting means 3 is replaced by the burst signal phase detectingmeans 10.

In the video signal processing circuit of the sixth embodiment, theconfiguration and operation of the burst signal phase detecting means 10and the color demodulating means 110 are the same as in the fourthembodiment, and the configuration and operation of the other parts arethe same as in the fifth embodiment.

According to the sixth embodiment, the phase difference calculationmeans 81 calculates a frame-to-frame phase error from the colorsubcarrier phase information in a composite signal for any of aplurality of television broadcast systems or for a non-standard signal;a phase correction is obtained to provide a frame-to-frame colorsubcarrier phase difference of 180°; and Y/C separation is carried outafter the sampling phase of the composite signal is corrected bysampling phase conversion. Accordingly, excellent three-dimensional Y/Cseparation is carried out, regardless of the frame-to-frame phaserelationship, even with a non-standard signal, and degradation ofpicture quality after Y/C separation can be prevented. The colorsubcarrier phase information is obtained from the burst signal phasedetection means that generates a color reference signal for colordemodulation, so that excellent Y/C separation is carried out withoutany great increase in the size of the circuitry, and degradation ofpicture quality after Y/C separation can be prevented.

Seventh Embodiment

In the first to third embodiments and the fifth embodiment, a compositesignal is input; excellent two-dimensional or three-dimensional Y/Cseparation is carried out, regardless of the line-to-line orframe-to-frame phase relationship, even with a non-standard signal; andY and C signals are obtained. In the seventh embodiment, a video signaldisplay device receives a composite video signal and, after Y/Cseparation, displays the Y and C signals.

FIG. 27 is a block diagram showing an example of the structure of thevideo signal display device of the seventh embodiment, based the firstembodiment shown in FIG. 1, denoting elements identical to elements inFIG. 1 by the same reference numerals. As shown in FIG. 27, the videosignal display apparatus of the seventh embodiment comprises an A/Dconversion means 1, a clock generating means 2, a burst phase detectingmeans 3, a phase difference calculation means 4, a sync separation means5, a timing signal generating means 6, a broadcast system setting means7, a sampling phase conversion means 8, a Y/C separation means 9, adisplay processing means 200, and a display means 201.

Video signal display devices for displaying signals from televisionbroadcast systems, VTRs, DVDs, video games, and the like generally havean input terminal for a composite signal; the input composite signal isconverted to a digital signal; Y/C separation is performed; and theresulting Y and C signals are processed and displayed as an image. Thevideo signal display device of the seventh embodiment differs from thevideo signal processing circuit of the first embodiment (see FIG. 1) inthat a display processing means 200 and a display means 201 forprocessing the Y and C signals output from the Y/C separation means 9are provided to display a video image, following Y/C separation. Theconfiguration and operation of the parts other than the displayprocessing means 200 and display means 201 are the same as in the firstembodiment described above.

Display Processing Means 200

The display processing means 200 receives the Y and C signals separatedby the Y/C separation means 9, obtains R-Y and B-Y color differencesignals through color demodulation of the C signal in accordance withthe Y and C signals, converts the color difference signals to, forexample, red, green, and blue (RGB) signals, performs further signalprocessing, such as scaling processing, to convert these signals todisplay signals, and outputs the display signals to the display means201.

Display Means 201

The display means 201 displays the signals output from the displayprocessing means 200. A video image based on the Y and C signalsseparated by the Y/C separation means 9 is thereby displayed.

According to the seventh embodiment, the sampling phase of the compositesignal for any of a plurality of television broadcast systems or for anon-standard signal is corrected through sampling phase conversion, thenY/C separation is carried out. Excellent Y/C separation is carried out,regardless of the line-to-line phase relationship, even with anon-standard signal, and a video image based on the separated Y and Csignals is displayed. Accordingly, a superior video image is displayed,without luminance-chrominance crosstalk, dot crawl, and other types ofpicture quality degradation.

The seventh embodiment as described above differs from the firstembodiment in that the display processing means 200 and display means201 are provided to display the output from the Y/C separation means 9,but the same effect is produced if the display processing means 200 anddisplay means 201 are added to the second embodiment, as shown in FIG.28, or to the third embodiment, as shown in FIG. 29, or if the displayprocessing means 200 and display means 201 are provided following theY/C separation means 83 in the fifth embodiment, as shown in FIG. 30.

Eighth Embodiment

In the fourth and sixth embodiments, a composite signal is input;excellent two-dimensional or three-dimensional Y/C separation isperformed, regardless of the line-to-line or frame-to-frame phaserelationship, even with a non-standard signal, and Y and C signals areobtained from the input composite signal; after color demodulation, aset of signals including the Y signal and R-Y and B-Y signals isobtained. In the eighth embodiment, a video signal display devicereceives an input composite signal and displays the Y signal and the R-Yand B-Y signals resulting from Y/C separation and color demodulation.

FIG. 31 is a block diagram showing an example of the structure of thevideo signal display device of the eighth embodiment, based on thefourth embodiment shown in FIG. 18, denoting elements identical toelements shown in FIG. 18 by the same reference numerals. As shown inFIG. 31, the video signal display device according to the eighthembodiment comprises an A/D conversion means 1, a clock generating means2, a phase difference calculation means 4, a sync separation means 5, atiming signal generating means 6, a broadcast system setting means 7, asampling phase conversion means 8, a Y/C separation means 9, a burstsignal phase detecting means 10, a color demodulating means 110, adisplay processing means 202, and a display means 201.

Video signal display devices for displaying signals from televisionbroadcast systems, VTRs, DVDs, video games, and the like generally havean input terminal for a composite signal; the input composite signal isconverted to a digital signal; Y/C separation and color demodulation arecarried out; and the resulting Y, R-Y, and B-Y signals are displayed asan image. The video signal display device of the eighth embodimentdiffers from the video signal processing circuit of the fourthembodiment (see FIG. 18) in that the display processing means 202 forprocessing the Y signal output from the Y/C separation means 9 and theR-Y and B-Y signals output from the color demodulating means 110 and thedisplay means 201 are provided to display a video image following Y/Cseparation and color demodulation. The configuration and operation ofthe parts other than the display processing means 202 and display means201 are the same as in the fourth embodiment, and the configuration andoperation of the display means 201 are the same as in the seventhembodiment described above.

Display Processing Means 202

The display processing means 202 receives the Y signal separated by theY/C separation means 9 and the R-Y and B-Y signals output from the colordemodulating means 110, converts the Y, R-Y, and B-Y signals to RGBsignals, for example, performs further signal processing, such asscaling processing, to convert these signals to display signals, andoutputs the display signals to the display means 201. The display means201 displays the display signals from the display processing means 202.A video image based on the Y signal separated by the Y/C separationmeans 9 and the R-Y and B-Y signals output from the color demodulatingmeans 110 is thereby displayed.

According to the eighth embodiment, the sampling phase of the compositesignal for any of a plurality of television broadcast systems or for anon-standard signal is corrected through sampling phase conversion, thenY/C separation is carried out. Excellent Y/C separation is carried out,regardless of the line-to-line phase relationship, even with anon-standard signal, and a video image based on the Y, R-Y, and B-Ysignals is displayed. Accordingly, a superior video image is displayed,without luminance-chrominance crosstalk, dot crawl, and other types ofpicture quality: degradation.

The eighth embodiment described above differs from the fourth embodimentin that the display processing means 202 and display means 201 areprovided to display the output from the Y/C separation means 9 and colordemodulating means 110, but the same effect is produced if the displayprocessing means 202 and display means 201 are provided following theY/C separation means 83 and color demodulating means 110 of the sixthembodiment, as shown in FIG. 32.

Ninth Embodiment

In the first to third embodiments and the fifth embodiment, a compositesignal is input; excellent two-dimensional or three-dimensional Y/Cseparation is performed, regardless of the line-to-line orframe-to-frame phase relationship, even with a non-standard signal; andY and C signals are obtained. In the ninth embodiment, a video signalrecording device receives an input composite signal and records a videosignal based on the Y and C signals resulting from Y/C separation.

FIG. 33 is a block diagram showing an example of the structure of thevideo signal recording device of the ninth embodiment, based on thefirst embodiment shown in FIG. 1, denoting elements identical toelements in FIG. 1 by the same reference numerals. As shown in FIG. 33,the video signal recording device according to the ninth embodimentcomprises an A/D conversion means 1, a clock generating means 2, a burstphase detecting means 3, a phase difference calculation means 4, a syncseparation means 5, a timing signal generating means 6, a broadcastsystem setting means 7, a sampling phase conversion means 8, a Y/Cseparation means 9, a recording signal processing means 300, and arecording means 301.

Video signal recording devices for recording signals from televisionbroadcast systems, VTRs, DVDs, video games, and the like generally havean input terminal for a composite signal; the input composite signal isconverted to a digital signal; Y/C separation is performed; and theresulting Y and C signals are processed and recorded as an image. Thevideo signal recording device of the ninth embodiment adds to the videosignal processing circuit of the first embodiment (see FIG. 1) furthercircuitry to record the signals after Y/C separation, the addedcircuitry comprising the recording signal processing means 300 forprocessing the Y and C signals output from the Y/C separation means 9,and the recording means 301. The configuration and operation of theparts other than the recording signal processing means 300 and recordingmeans 301 are the same as in the first embodiment.

Recording Signal Processing Means 300

The recording signal processing means 300 receives the Y and C signalsseparated by the Y/C separation means 9; converts them to RGB signals orto Y, R-Y, and B-Y signals, for example; performs signal processingnecessary for recording, including an encoding process such as MPEG2image compression and a recording modulation process; and outputs arecording signal to the recording means 301.

Recording Means 301

The recording means 301 records the recording signal from the recordingsignal processing means 300 in a video tape cassette, DVD, hard disk, orother recording media. A video signal based on the Y and C signalsseparated by the Y/C separation means 9 is recorded on the recordingmedium.

According to the ninth embodiment, the sampling phase of the compositesignal for any of a plurality of television broadcast systems or for anon-standard signal is corrected through sampling phase conversion, thenY/C separation is carried out. Excellent Y/C separation is carried out,regardless of the line-to-line phase relationship, even with anon-standard signal, and a video signal based on the resulting Y and Csignals is recorded. Accordingly, a good video signal can be recordedwithout picture degradation such as luminance-chrominance crosstalk anddot crawl.

The ninth embodiment as described above adds the recording signalprocessing means 300 and recording means 301 to the first embodiment torecord the output from the Y/C separation means 9, but the same effectis produced if the recording signal processing means 300 and recordingmeans 301 are added to the second embodiment, as shown in FIG. 34, or tothe third embodiment, as shown in FIG. 35, or if the recording signalprocessing means 300 and recording means 301 are provided following theY/C separation means 83 of the fifth embodiment, as shown in FIG. 36.

Tenth Embodiment

In the fourth and sixth embodiments, a composite signal is input;excellent two-dimensional or three-dimensional Y/C separation isperformed, regardless of the line-to-line or frame-to-frame phaserelationship, even with a non-standard signal; and after colordemodulation, a Y signal and R-Y and B-Y signals are obtained. In thetenth embodiment, a video signal recording device receives an inputcomposite signal and records a video signal based on the Y, R-Y, and B-Ysignals after Y/C separation and color demodulation.

FIG. 37 is a block diagram showing an example of the structure of thevideo signal recording device of the tenth embodiment, based on thefourth embodiment shown in FIG. 18, denoting elements identical toelements shown in FIG. 18 by the same reference numerals. As shown inFIG. 37, the video signal recording device according to-the tenthembodiment comprises an A/D conversion means 1, a clock generating means2, a phase difference calculation means 4, a sync separation means 5, atiming signal generating means 6, a broadcast system setting means 7, asampling phase conversion means 8, a Y/C separation means 9, a burstsignal phase detecting means 10, a color demodulating means 110, arecording signal processing means 302, and a recording means 301.

Video signal recording devices for recording signals from televisionbroadcast systems, VTRs, DVDs, video games, and the like generally havean input terminal for a composite signal; the input composite signal isconverted to a digital signal; Y/C separation and color demodulation areperformed; and Y, R-Y, and B-Y signals are recorded as an image. Thevideo signal recording device of the tenth embodiment adds to the videosignal processing circuit of the fourth embodiment (see FIG. 18) furthercircuitry to record the signals after Y/C separation and colordemodulation, the added circuitry being the recording signal processingmeans 302 for processing the Y signal output from the Y/C separationmeans 9 and the R-Y and B-Y signals output from the color demodulatingmeans 110, and the recording means 301. The configuration and operationof the parts other than the recording means 301 and recording signalprocessing means 302 are the same as in the fourth embodiment, and theconfiguration and operation of the recording means 301 are the same asin the ninth embodiment.

Recording Signal Processing Means 302

The recording signal processing means 302 receives a Y signal separatedby the Y/C separation means 9 and R-Y and B-Y signals output from thecolor demodulating means 110, performs signal processing necessary forrecording, including an encoding process such as MPEG2 image compressionand a recording modulation process, in accordance with the Y, R-Y, andB-Y signals; and outputs a recording signal to the recording means 301.The recording means 301 records the recording signal from the recordingsignal processing means 302 on a recording medium.

According to the tenth embodiment, the sampling phase of the compositesignal for any of a plurality of television broadcast systems or for anon-standard signal is corrected through sampling phase conversion, thenY/C separation is carried out. Excellent Y/C separation is carried out,regardless of the line-to-line phase relationship, even with anon-standard signal, and a video signal based on the resulting Y, R-Y,and B-Y signals is recorded. Accordingly, a good video signal can berecorded without picture degradation such as luminance-chrominancecrosstalk and dot crawl.

The tenth embodiment as described above adds the recording signalprocessing means 302 and recording means 301 to the fourth embodiment torecord outputs from the Y/C separation means 9 and color demodulatingmeans 110, but the same effect is produced if the recording signalprocessing means 302 and recording means 301 are added after the Y/Cseparation means 83 and color demodulating means 110 of the sixthembodiment, as shown in FIG. 38.

1. A video signal processing circuit that samples an analog compositevideo signal, converts the composite video signal to a digital signal,and processes the composite video signal by using a prescribed clocksignal, comprising: a clock generating means generating the prescribedclock signal; a phase detecting means detecting color subcarrier phaseinformation in each line of the composite video signal; a phasedifference calculation means calculating a phase difference betweenphase information obtained from the phase detecting means and aprescribed reference phase, calculating a phase correction from thephase difference, and outputting the phase correction; a sampling phaseconversion means correcting the phase at which the composite videosignal is sampled according to the phase correction output from thephase difference calculation means; and a luminance/chrominance (Y/C)separation means separating a luminance signal and a chrominance signalfrom the composite video signal output from the sampling phaseconversion means.
 2. The video signal processing circuit of claim 1,wherein the phase detecting means detects a burst phase in each line ofthe composite video signal and outputs the burst phase as the colorsubcarrier phase information of the line.
 3. The video signal processingcircuit of claim 1, further comprising a color demodulating meansdemodulating the chrominance signal separated by the Y/C separationmeans according to a color subcarrier reference signal to obtain colordifference signals, wherein: the phase detecting means detects the burstphase in each line of the composite video signal, outputs the burstphase as the color subcarrier phase information of the line, andgenerates the color subcarrier reference signal according to thedetected burst phase.
 4. The-video signal processing circuit of claim 1,wherein the prescribed reference phase is the reference phase of atarget line determined by a prescribed fixed phase value and the phaseinformation of the target line; and the phase difference calculationmeans calculates a phase difference between the phase information of acertain line and the reference phase of the target line, the certainline being separated by a prescribed number of lines or fields from thetarget line.
 5. The video signal processing circuit of claim 4, whereinthe phase difference calculation means comprises: a delaying meansapplying a delay of the prescribed number of lines or fields to thephase information from the phase detecting means; a phase errorcalculation means obtaining a phase difference between the phaseinformation of the certain line and the reference phase of the targetline, including phase information of the target line, as a phase error;and a correction conversion means converting the phase error to a phasecorrection with reference to one period of the clock generated by theclock generating means.
 6. The video signal processing circuit of claim1, wherein the prescribed reference phase includes a fixed phase valuepredetermined by the line position of the composite video signal; andthe phase difference calculation means calculates a phase differencebetween the phase information and the fixed reference phase.
 7. Thevideo signal processing circuit of claim 6, wherein the phase differencecalculation means comprises: a delaying means applying a delay of theprescribed number of lines or fields to the phase information from thephase detecting means; a phase error calculation means obtaining both aphase difference between the phase information of the target line andthe fixed reference phase and a phase difference between the phaseinformation of the certain line separated by a prescribed number oflines or fields from the target line and the fixed reference phase asphase errors; and a correction conversion means converting the phaseerror to a phase correction with reference to one period of the clock.8. The video signal processing circuit of claim 6, wherein the phasedifference calculation means comprises: a phase error calculation meansobtaining a phase difference between the phase information from thephase detecting means and the fixed reference phase as a phase error;and a correction conversion means converting the phase error to a phasecorrection with reference to one period of the clock.
 9. The videosignal processing circuit of claim 1, wherein the sampling phaseconversion means comprises: a delaying means applying a delay of aprescribed number of lines or fields to the composite video signal; anda phase correction means correcting the phase at which the compositevideo signal of a certain line separated by a prescribed lines or fieldsfrom the target line, or the composite video signal of the target lineand the composite video signal of the prescribed line, is sampled, inaccordance with the output from the phase difference calculation means.10. The video signal processing circuit of claim 9, wherein the phasecorrection means comprises: a coefficient generating means generatingcoefficients of a filter having a group delay corresponding to theoutput from the phase difference calculation means; and a filter meansperforming filtering of the composite video signal in accordance withthe coefficients.
 11. The video signal processing circuit of claim 9,wherein the phase correction means comprises: a plurality of delayingmeans applying a certain delay to the composite video signal; and aselection means selecting the output of the plurality of delaying meansin accordance with the output from the phase difference calculationmeans.
 12. The video signal processing circuit of claim 9, wherein thephase correction means comprises: a coefficient generating meansgenerating an interpolation filter coefficient for obtaining the valueof a point corresponding to a position offset from the sampling positionof the composite video signal by the phase difference corresponding tothe output of the phase difference calculation means; and a filter meansperforming filtering of the composite video signal in accordance withthe coefficient.
 13. The video signal processing circuit of claim 1,further comprising: an A/D conversion means converting the input analogcomposite video signal to a digital composite video signal, the samplingphase conversion means comprising: a clock phase correction meanscorrecting the phase of the clock generated by the clock generatingmeans in accordance with the output from the phase differencecalculation means; and a delaying means applying a delay of a prescribednumber of lines or fields to the digitized composite video signal;wherein the A/D conversion means converts the composite video signal toa digital signal by using a clock with a phase corrected by the clockphase correction means.
 14. The video signal processing circuit of claim1, wherein the Y/C separation means separates the luminance signal andthe chrominance signal from the composite video signal by means of aline comb filter or frame comb filter, by using the composite videosignal output from the sampling phase conversion means in a plurality oflines.
 15. The video signal processing circuit of claim 1, wherein theclock generating means generates a clock signal with a frequency equalto an integer multiple of 13.5 MHz, regardless of the televisionbroadcast system of the composite video signal, for the processing ofthe composite video signal.
 16. The video signal processing circuit ofclaim 1, wherein the clock generating means generates a burst lockedclock in phase with the burst signal in the composite video signal forthe processing of the composite video signal.
 17. The video signalprocessing circuit of claim 1, wherein the clock generating meansgenerates a line locked clock in phase with the horizontal sync signalin the composite video signal for the processing of the composite videosignal.
 18. The video signal processing circuit of claim 1, furthercomprising a television broadcast system setting means specifying abroadcast system of the composite video signal, wherein: the phasedetecting means detects a color subcarrier phase in accordance with thebroadcast system specified by the television broadcast system settingmeans; the phase difference calculation means obtains the phasedifference in accordance with the specified television broadcast system;and the Y/C separation means separates the luminance signal and thechrominance signal from the composite video signal in accordance withthe specified television broadcast system.
 19. A video signal displaydevice comprising the video signal processing circuit of claim
 1. 20. Avideo signal recording device comprising the video signal processingcircuit of claim 1.